Improve document symbol hierarchy to match rust-analyzer layout

[JoshuaBatty]

Description

Changes document symbols to show the nested outline of a file with type information, matching rust-analyzer's outline view structure.

closes #6100

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.

[alfiedotwtf]

Just curious why both range and selection_range are needed if they're the same values?

[JoshuaBatty]

Just curious why both range and selection_range are needed if they're the same values?

I just put that there as a placeholder for now, still need to sort that and quite a bit more out. Probably at least a few more days of work left to get this PR ready. I'd expect this part to change before i'm ready to open up the PR for review.

[maxtalantsev]

cool