MINOR: Make Checkstyle more strict, restore global code quality checks to 2018

[gharris1727]

The connect suppressions are more permissive than necessary, because suppressions were added to the file and then not later removed. Most notably:

• KAFKA-10070: parameterize Connect unit tests to remove code duplication #10299 removed the WithTopicCreation test variants
• KafkaConfigBackingStore got an overhaul in KAFKA-10000: Zombie fencing (KIP-618) #11779 that split up a really large method, and I think solved several warnings at the same time.
• The ParameterNumber restriction was relaxed from 10 to 13 during KIP-98
• The ClassDataAbstraction restriction was relaxed from 20 to 25 in KIP-222 - Add Consumer Group operations to Admin API #4454
• BooleanExpressionComplexity was relaxed from 4 to 5 in KAFKA-4923: Add Exaclty-Once Semantics to Streams (testing) #2974
• The NPathComplexity was never relaxed. I think the RestClient and RestServer are borderline, and happen to be safe right now.

Recently PRs have been relaxing the global checkstyle limits instead of adding suppressions:

• The ClassFanOutComplexity was relaxed from 50 to 52 in KAFKA-14412: Decouple RocksDB access from CF #15105
• The MethodLength restriction was relaxed from 150 to 170 in KAFKA-15355: Message schema changes #14290

I noticed this lead to the DistributedHerder no longer needing a MethodLength suppression. While the heuristics are arbitrary, in the interest in preventing the "code quality ratchet" from slipping, I reverted those changes and added the necessary suppressions.

Committer Checklist (excluded from commit message)

• Verify design and implementation
• Verify test coverage and CI build status
• Verify documentation (including upgrade notes)

[gharris1727]

I realized that it was a bit silly both manually auditing these, and only fixing the Connect ones. I've instead addressed all of the unused suppressions by building a little audit script.

It finds suppressions which:

1. Don't use the full name of the check, and instead use a shortened form
2. Include the same check and the same class as another suppression
3. Are missing, and the class has errors (this is what checkstyle normally does)
4. Are missing, the class has errors for, but a shorter class name is listed in the suppressions
5. Are present, but the named class doesn't generate the corresponding error

It's a rough-and-ready script, and doesn't handle the more powerful regexes in the suppressions file, only the basic ones composed of a single group. There are carve outs for the powerful regex hardcoded-in that prevent them from emitting spurious errors.

I'll do my best to keep this rebased, but I would appreciate a quick review as people are currently adding new suppressions while this is open :)

[gharris1727]

While I can sorta keep up with the stream of merge conflicts in this one PR, I realize now that completely rewriting nearly every line in suppressions.xml is going to generate a ton of merge conflicts for everyone else. This might to lead to build breakages, so I'm hesitating on merging this.

I'm if i should merge this as-is, close it un-merged, or scale it back to just the changes in checkstyle.xml (lowering the limits).

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