feat(java 21): allow toplevel method declarations

[brandonspark]

What:

This PR allows top-level statements to comprise of method declarations.

Why:

This is because Java 21 adds "unnamed classes", which means such classes can now be "anonymous", and now method declarations can just exist at the top level. This is a Java 21 feature that the grammar should aim to accommodate.

How:

Just made a new hidden nonterminal called toplevel_statements, which may be a method_declaration.

I could have changed statement itself, but statement is used at places that are not the top level, and this causes conflicts.

Worth noting that the state count increases by about 100. That's not a whole lot, so I'm cool with it, but worth noting.

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).

[amaanq]

Can you combine all your PRs into one PR, separate the changes by commit instead, then do one generate at the end as its own commit? This way the repo isn't unnecessarily bloated with changes to parser.c

[aryx]

To be honest I prefer to have separate PRs for each feature added.
The problem is that we should not have those generated parser.c code in the repo in the first place ... They make the reviewing process more difficult. I sometimes can't even review PR on github because the diff is 1M LOC.
I don't know when @maxbrunsfeld will decide we can remove those generated files.

[amaanq]

To be honest I prefer to have separate PRs for each feature added. The problem is that we should not have those generated parser.c code in the repo in the first place ... They make the reviewing process more difficult. I sometimes can't even review PR on github because the diff is 1M LOC. I don't know when @maxbrunsfeld will decide we can remove those generated files.

I can agree w/ having a PR per feature, but the issue is when each PR has generated files it unnecessarily adds to the repo size when one generation after all the PRs would be much better.

We can't remove the files for now, ideally using something like GH artifacts to host generated files would be best, but we're not there yet

[brandonspark]

@aryx this can be merged now