[java] Make naming conventions rule skip unnamed variables

[oowekyala]

Describe the PR

I think the best solution here is not to allow _ through the regexes as suggested in #4954 but rather to always ignore these variables. That's because I don't think the rule should ever be used to disallow unnamed variables. We would otherwise be restricting a useful language feature, and anyone changing the convention would need to explicitly takes care of special casing this identifier.

Related issues

• Fix [java] LocalVariableNamingConventions should allow unnamed variables by default #4954
• Fix [java] FormalParameterNamingConventions should accept unnamed parameters by default #5028

Ready?

• Added unit tests for fixed bug/feature
• Passing all unit tests
• Complete build ./mvnw clean verify passes (checked automatically by github actions)
• Added (in-code) documentation (if needed)

[pmd-test]

	1 Message
📖	No regression tested rules have been changed.
✅	Compared to master: This changeset changes 0 violations, introduces 0 new violations, 0 new errors and 0 new configuration errors, removes 7 violations, 0 errors and 0 configuration errors. Download full report as build artifact
✅	Compared to master: This changeset changes 0 violations, introduces 0 new violations, 0 new errors and 0 new configuration errors, removes 7 violations, 0 errors and 0 configuration errors. Download full report as build artifact

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[jsotuyod]

We should probably add a parsing test for pre-Java9 to ensure that @Name = "_" but @Unnamed = false.

Apart from that this looks great to merge, thanks!

[adangel]

We should probably add a parsing test for pre-Java9 to ensure that @Name = "_" but @Unnamed = false.

I'll add a test for that and merge it afterwards.