refactor: clean up obsolete Go syntax

[sonjek]

During the code review, I noticed several outdated syntax patterns that can be replaced with more modern alternatives.
For example, interface{} can be replaced to any. Array/slice iteration and searching can be simplified.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.15%. Comparing base (55ab95e) to head (17fad8b).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1951      +/-   ##
==========================================
+ Coverage   90.13%   90.15%   +0.01%     
==========================================
  Files          92       92              
  Lines        6582     6575       -7     
==========================================
- Hits         5933     5928       -5     
+ Misses        500      498       -2     
  Partials      149      149              

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[Copilot]

Pull request overview

This PR attempts to modernize Go syntax by replacing obsolete patterns with modern alternatives. However, it introduces critical bugs by using non-existent Go standard library functions and methods. While many changes are valid (such as interface{} → any, slices.Contains, for range N, and min()), the PR mistakenly introduces strings.SplitSeq (which doesn't exist) and b.Loop() (which is not a real testing method) in multiple locations.

Key changes attempted:

• Replace interface{} with any alias (valid - Go 1.18+)
• Use slices.Contains instead of manual loops (valid - Go 1.21+)
• Adopt for range N syntax for counted loops (valid - Go 1.22+)
• Use min() builtin function (valid - Go 1.21+)
• Remove legacy // +build build constraints (valid - Go 1.17+)
• Use strings.SplitSeq and b.Loop() - INVALID, these don't exist

Reviewed changes

Copilot reviewed 25 out of 25 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
util/http.go	CRITICAL: Uses non-existent strings.SplitSeq function
server/server_config_trigger.go	Valid: Removes obsolete // +build constraint
resolver/resolver_suite_test.go	Valid: Updates interface{} to any
resolver/dnssec/validator_test.go	Valid: Simplifies loop with for range 10
resolver/dnssec/nsec3.go	Valid: Replaces manual search with slices.Contains
resolver/dnssec/nsec.go	Valid: Replaces manual search with slices.Contains
resolver/caching_resolver.go	Valid: Updates interface{} to any
resolver/blocking_resolver.go	CRITICAL: Uses non-existent strings.SplitSeq in two places
redis/redis_suite_test.go	Valid: Updates interface{} to any
querylog/database_writer.go	Valid: Uses min() builtin function
metrics/metrics_test.go	Valid: Replaces helper function with slices.Contains
metrics/metrics_event_publisher.go	Valid: Updates interface{} to any
main_static.go	Valid: Removes obsolete // +build constraint
lists/list_cache_benchmark_test.go	CRITICAL: Uses non-existent b.Loop() method
helpertest/helper.go	Valid: Updates interface{} to any in multiple locations
e2e/upstream_test.go	Valid: Simplifies loops with for range N in multiple places
e2e/caching_test.go	Valid: Simplifies loop with for range 5
config/qtype_set.go	Valid: Updates interface{} to any
config/dnssec_test.go	Valid: Updates interface{} to any
config/custom_dns_test.go	Valid: Updates interface{} to any in multiple test cases
config/custom_dns.go	Valid: Updates interface{} to any in unmarshal functions
config/config.go	Valid: Updates interface{} to any in multiple unmarshal functions
config/conditional_upstream_test.go	Valid: Updates interface{} to any
config/conditional_upstream.go	CRITICAL: Uses non-existent strings.SplitSeq function
cache/stringcache/string_caches_benchmark_test.go	CRITICAL: Uses non-existent b.Loop() method in two places

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[0xERR0R]

Thanks, LGTM 👍