Add inlay hints for function parameters

[JoshuaBatty]

Description

Inlay hints are now displayed in function parameter locations if a variable with the same name is not present. This should be identical to the behaviour of rust-analyzer. The inlay_hints benchmark is slower because we are now also calculating inlay hints for function_params and variable decls in the same iteration. See screen shot below for all supported types.

closes #5196

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 #6513 will degrade performances by 82.78%

_{Comparing josh/inlay_hints_function_params (a91181d) with master (e1546f6)}

Summary

❌ 2 regressions
✅ 20 untouched benchmarks

⚠️ Please fix the performance issues or acknowledge them on CodSpeed.

Benchmarks breakdown

	Benchmark	master	josh/inlay_hints_function_params	Change
❌	document_symbol	4.4 ms	5.3 ms	-17.66%
❌	inlay_hints	3.2 ms	18.6 ms	-82.78%