fix: Multiple jdtls LSPs eating memory in java monorepos

[stevoland]

What does this PR do?

In monorepos, starts jdtls at the project root* to let it discover and handle all submodules with a single process.

*Uses the project markers already used for kotlin-ls.

There's some complexity which I think is necessary to handle all cases - hopefully explained by the inline comments.

Fixes: #11368

How did you verify your code works?

Ran in gradle monorepo, reading files from multiple modules:

Before:

LSP
jdtls module-a
jdtls module-b
jdtls module-c

After:

LSP
jdtls

Made edits and got correct diagnostics in tool results.

Ran in single project repo, made edits

Thanks

[github-actions]

The following comment was made by an LLM, it may be inaccurate:

No duplicate PRs found

[ChrisJamesHassell]

++ Can we get a stamp on this? I stopped using OpenCode entirely because of this bug.

[stevoland]

Thanks @ChrisJamesHassell. Hard times round here :)

fwiw we fixed with a plugin that disables jdtls and reimplements.

It's part of a larger plugin but you'll get the idea. Just for our case where there's always a build.gradle at project root: https://gist.github.com/stevoland/f0f3c5ac12755e48db8459c8ff535cdd

[jiayaoO3O]

Is it possible to also construct a plugin for Maven multi-module projects?