Add find all references feature to the language server.

[JoshuaBatty]

Description

closes #5961

See video below for how it's used.

Find.references.mp4

Checklist

• I have linked to any relevant issues.
• I have commented my code, particularly in hard-to-understand areas.
• I have updated the documentation where relevant (API docs, the reference, and the Sway book).
  • If my change requires substantial documentation changes, I have requested support from the DevRel team
• I have added tests that prove my fix is effective or that my feature works.
• I have added (or requested a maintainer to add) the necessary Breaking* or New Feature labels where relevant.
• I have done my best to ensure that my PR adheres to the Fuel Labs Code Review Standards.
• I have requested a review from the relevant team or maintainers.

[codspeed-hq]

CodSpeed Performance Report

Merging #6512 will not alter performance

_{Comparing josh/references (881ac35) with master (4830d00)}

Summary

✅ 21 untouched benchmarks

🆕 1 new benchmarks

Benchmarks breakdown

	Benchmark	master	josh/references	Change
🆕	find_all_references	N/A	46.3 ms	N/A

[sdankel]

Nice one!