Add RemovePrivateFieldUnderscores recipe

[jhl221123]

What's changed?

This recipe removes prefix or suffix underscores from private class field names. This helps enforce modern Java coding standards.

For clarity and consistency, the recipe also adds a qualifier to all updated field accesses. This prevents ambiguity with local variables and ensures a uniform style throughout the class.

What's your motivation?

• Fixes #630

Checklist

• [X] I've added unit tests to cover both positive and negative cases
• [X] I've read and applied the recipe conventions and best practices
• [X] I've used the IntelliJ IDEA auto-formatter on affected files

[timtebeek]

Let us know if you'd need any guidance @jhl221123 ! Perhaps this session could help you get started: https://www.moderne.ai/content-library/introduction-to-openrewrite

[dsgrieve]

Another case:

String foo(String bar) {
    String _bar = bang(bar); 
    // ... do something else with bar ... 
    return _bar;
}

In this case, I would expect no change.

[jhl221123]

Thanks for the detailed feedback, @dsgrieve. I believe I've addressed everything now. Ready for another look when you have a moment.

[dsgrieve]

Sorry. I keep stumbling upon use cases. Be aware of JEP 456 which allows an _ to be used as an un-named variable.

[jhl221123]

@dsgrieve No problem at all, and thank you for catching these important edge cases! I've pushed an update to handle it. Please let me know if you spot anything else.

[greg-at-moderne]

Nice work on the recipe. Don't worry about the timing, we are not in a hurry in any way ;)

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