☂️ Improved code nav for locals and parameters

[varungandhi-src]

Subtask of https://github.com/sourcegraph/sourcegraph/issues/58005

The web frontend can automatically do search-based code nav for locals and params based purely on a SCIP document. Adding support for locals & params in more languages enables better code nav experience without any more backend changes.

Language support

• Java https://github.com/sourcegraph/sourcegraph/pull/57620 (supersedes Squirrel)
• Go
• Scala (new)
• Kotlin

Initially, Rust was meant to be done in this quarter, but we're postponing it because of the additional complexity and lower usage.

Bug fixes

• https://github.com/sourcegraph/sourcegraph/issues/57791
• https://github.com/sourcegraph/sourcegraph/issues/58548 (not 100% sure yet if the issue is in tree-sitter or in frontend code)

Migrate queries from Squirrel to scip-syntax

Cancelled as it requires more time.

• Python
• JavaScript
• TypeScript

Stretch goals

• https://github.com/sourcegraph/sourcegraph/issues/58495
• Migrate other languages from Squirrel to scip-syntax: C, C#, Ruby, Starlark
• Stop emitting non-local symbol names for local entities (similar to #57791) for MATLAB and Perl
• https://github.com/sourcegraph/sourcegraph/issues/59656
• https://github.com/sourcegraph/sourcegraph/issues/59629