feat(builtins): add gotests support in code actions

[joshrwolf]

Adds gotests as a builtin code action with 2 operating modes:

1. package tests (available when cursor positioned over a package_clause)
2. function test (available when cursor positioned over a identifier)

This PR is heavily influenced by the awesome work in #1339.

[jose-elias-alvarez]

This looks good, thanks! Can you go ahead and remove the extra print statements and also let me know how I can test this in case I have to investigate issues in the future?

[joshrwolf]

thanks for the 👀! is there a designated place in the codebase for leaving testing information (like the meta.notes section?), or would you prefer it in this PR

[jose-elias-alvarez]

Just in this PR is fine - I found the approach in #1339 helpful to review the PR and then to test an additional change.

[ArtAndreev]

Can we get it merged, please? Also docs are needed to be updated, need fixing treesitter deprecations.