Parent issue: #19604

Description

Add Checkstyle checks for all rules under §3.5 - Modifiers of the OpenJDK Java Style Guidelines v6.

Rules covered

From §3.5 - Modifiers:

1. Modifiers should go in the order: access modifier, abstract, static, final, transient, volatile, default, synchronized, native, strictfp — ModifierOrder Check
2. Modifiers should not be written out when they are implicit (e.g., interface methods should not be declared public or abstract, nested enums/interfaces should not be declared static) — RedundantModifier Check
3. Method parameters and local variables should not be declared final unless it improves readability — cannot be enforced (subjective guideline)
4. Fields should be declared final unless there is a compelling reason to make them mutable — cannot be enforced (subjective guideline)

Checks to add to openjdk_checks.xml

TreeWalker-level:

<module name="ModifierOrder"/>

<module name="RedundantModifier"/>