refactor: use b.Loop() to simplify the code and improve performance

[promalert]

These changes use b.Loop() to simplify the code and improve performance
Supported by Go Team, more info: https://go.dev/blog/testing-b-loop

Before:

➜  alertmanager git:(main)  go test -run=^$ -bench=. ./matcher/parse   
goos: darwin
goarch: arm64
pkg: github.com/prometheus/alertmanager/matcher/parse
cpu: Apple M4
BenchmarkParseSimple-10     	 2337806	       500.5 ns/op
BenchmarkParseComplex-10    	  680635	      1950 ns/op
PASS
ok  	github.com/prometheus/alertmanager/matcher/parse	3.287s
➜  alertmanager git:(main) go test -run=^$ -bench=. ./notify    
goos: darwin
goarch: arm64
pkg: github.com/prometheus/alertmanager/notify
cpu: Apple M4
BenchmarkHashAlert-10    	 8728893	       126.3 ns/op
PASS
ok  	github.com/prometheus/alertmanager/notify	1.768s

After:

➜  alertmanager git:(main)  go test -run=^$ -bench=. ./matcher/parse         
goos: darwin
goarch: arm64
pkg: github.com/prometheus/alertmanager/matcher/parse
cpu: Apple M4
BenchmarkParseSimple-10     	 2392150	       493.4 ns/op
BenchmarkParseComplex-10    	  690627	      1762 ns/op
PASS
ok  	github.com/prometheus/alertmanager/matcher/parse	3.117s
➜  alertmanager git:(main) 
➜  alertmanager git:(main)  go test -run=^$ -bench=. ./notify                  
goos: darwin
goarch: arm64
pkg: github.com/prometheus/alertmanager/notify
cpu: Apple M4
BenchmarkHashAlert-10    	 8409073	       129.0 ns/op
PASS
ok  	github.com/prometheus/alertmanager/notify	1.343s

[Spaceman1701]

Just stumbled on this one and gave it a look. This looks totally fine to me, and the go.dev blog says that

The testing.B.Loop method is now the preferred way to write benchmarks:

One thing though: It looks like you missed inhibit_bench_test.go, silence_bench_test.go, and tls_transport_test.go. If we're going to make this change, I think we should do it everywhere to be consistent. Would you mind updating those as well?

[promalert]

Just stumbled on this one and gave it a look. This looks totally fine to me, and the go.dev blog says that

The testing.B.Loop method is now the preferred way to write benchmarks:

One thing though: It looks like you missed inhibit_bench_test.go, silence_bench_test.go, and tls_transport_test.go. If we're going to make this change, I think we should do it everywhere to be consistent. Would you mind updating those as well?

Thank you for your suggestions. However, I found that tls_transport_test.go doesn't have any modifications available.
The other two places have been updated. Please review again.

➜  alertmanager git:(main) ✗ go test -run=^$ -bench=. ./inhibit         
goos: darwin
goarch: arm64
pkg: github.com/prometheus/alertmanager/inhibit
cpu: Apple M4
BenchmarkMutes/1_inhibition_rule,_1_inhibiting_alert-10         	 1170290	       967.3 ns/op
BenchmarkMutes/10_inhibition_rules,_1_inhibiting_alert-10       	 1163775	       969.8 ns/op
BenchmarkMutes/100_inhibition_rules,_1_inhibiting_alert-10      	 1195722	       992.3 ns/op
BenchmarkMutes/1000_inhibition_rules,_1_inhibiting_alert-10     	  985664	      1176 ns/op
BenchmarkMutes/10000_inhibition_rules,_1_inhibiting_alert-10    	  997599	      1197 ns/op
BenchmarkMutes/1_inhibition_rule,_10_inhibiting_alerts-10       	 1057458	      1086 ns/op
BenchmarkMutes/1_inhibition_rule,_100_inhibiting_alerts-10      	 1057344	      1086 ns/op
BenchmarkMutes/1_inhibition_rule,_1000_inhibiting_alerts-10     	 1053831	      1085 ns/op
BenchmarkMutes/1_inhibition_rule,_10000_inhibiting_alerts-10    	 1068854	      1073 ns/op
BenchmarkMutes/100_inhibition_rules,_1000_inhibiting_alerts-10  	 1144471	      1010 ns/op
BenchmarkMutes/10_inhibition_rules,_last_rule_matches-10        	  227220	      5213 ns/op
BenchmarkMutes/100_inhibition_rules,_last_rule_matches-10       	   24458	     46616 ns/op
BenchmarkMutes/1000_inhibition_rules,_last_rule_matches-10      	    2451	    484289 ns/op
BenchmarkMutes/10000_inhibition_rules,_last_rule_matches-10     	     206	   5388896 ns/op
PASS
ok  	github.com/prometheus/alertmanager/inhibit	30.887s
➜  alertmanager git:(main) ✗ 
➜  alertmanager git:(main) ✗ go test -run=^$ -bench=. ./silence       
goos: darwin
goarch: arm64
pkg: github.com/prometheus/alertmanager/silence
cpu: Apple M4
BenchmarkMutes/1_silence_mutes_alert-10         	  368256	      3233 ns/op
--- BENCH: BenchmarkMutes/1_silence_mutes_alert-10
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
	... [output truncated]
BenchmarkMutes/10_silences_mute_alert-10        	  293503	      3794 ns/op
--- BENCH: BenchmarkMutes/10_silences_mute_alert-10
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
	... [output truncated]
BenchmarkMutes/100_silences_mute_alert-10       	  129474	      9183 ns/op
--- BENCH: BenchmarkMutes/100_silences_mute_alert-10
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
	... [output truncated]
BenchmarkMutes/1000_silences_mute_alert-10      	   14574	     79275 ns/op
--- BENCH: BenchmarkMutes/1000_silences_mute_alert-10
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
	... [output truncated]
BenchmarkMutes/10000_silences_mute_alert-10     	    1287	    891458 ns/op
--- BENCH: BenchmarkMutes/10000_silences_mute_alert-10
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
	... [output truncated]
BenchmarkQuery/100_silences-10                  	   85952	     13694 ns/op
--- BENCH: BenchmarkQuery/100_silences-10
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
	... [output truncated]
BenchmarkQuery/1000_silences-10                 	    8983	    130814 ns/op
--- BENCH: BenchmarkQuery/1000_silences-10
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
	... [output truncated]
BenchmarkQuery/10000_silences-10                	     715	   1729676 ns/op
--- BENCH: BenchmarkQuery/10000_silences-10
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
    mock.go:202: Mock Clock - Now([]) call, matched 0 traps
	... [output truncated]
PASS
ok  	github.com/prometheus/alertmanager/silence	12.547s
➜  alertmanager git:(main) ✗ 
➜  alertmanager git:(main) ✗ 

[Spaceman1701]

Thanks! This LGTM

We'll need to wait for a real maintainer to merge this.