Fix relative path resolution with temp manifests in LSP

[JoshuaBatty]

Description

The LSP now properly detects changes to Forc.toml files and updates build plans immediately, allowing for dynamic dependency modifications without requiring a server restart.

Previously, LSP was using old cached versions of the manifest files so new deps added were only being picked up and compiled after restarting the IDE.

Note, the change is only applied after the next did change event occurs, thus triggering a recompilation. A follow up PR to this will use the did_change_watched_files event to trigger recompilation automatically. I've opened an issue for that here #7103

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 #7079 will not alter performance

_{Comparing josh/lsp_workspace_bug (9eeb4d2) with master (760a2bf)}

Summary

✅ 22 untouched benchmarks

[tritao]

Lgtm

[sdankel]

Looks good!

[zees-dev]

LGTM 👍