feat(java 21): complete pattern matching for switch statements

[brandonspark]

What:

This PR adds in the last thing for supporting pattern matching for switch statements, as in Java 21, namely guards.

Why:

We should support the features of Java 21.

How:

Just added a guard nonterminal and put it in the right place, and added more tests for other Java 21 switch features.

Test plan:

tree-sitter test

Checklist:

• All tests pass in CI.
• There are sufficient tests for the new fix/feature.
• Grammar rules have not been renamed unless absolutely necessary.
• The conflicts section hasn't grown too much.
• The parser size hasn't grown too much (check the value of STATE_COUNT in src/parser.c).

[aryx]

need to rebase

[brandonspark]

@aryx rebased now

[amaanq]

Can you remove the regenerated files? Then it'd be nice to merge your 3 PRs and then generate after that

[brandonspark]

@amaanq done!

[brandonspark]

@amaanq well, this will also fail CI in the interim, unfortunately...

[brandonspark]

@amaanq it seems it's not possible to do "partial commits" with the regeneration step at a later time, because CI must pass before i merge. i think i'm just going to merge individually.

[amaanq]

okay, that's fine. you can add back the generated files.

[brandonspark]

@aryx could you merge this?