Replace Tokio Thread File Watcher with LSP Client File Watcher

[JoshuaBatty]

Description

This PR replaces our custom Tokio-based thread watcher for Forc.toml files with the built-in LSP didChangeWatchedFiles notification system. The changes:

• Remove the Tokio thread-based file watching system and associated cleanup code
• Implement client-side file watching registration during initialization
• Handle Forc.toml file changes through the LSP notification protocol
• Update tests to use the new notification system
• Simplify manifest syncing with a direct approach

This approach is more efficient as it leverages the client's native file watching capabilities rather than spawning a separate thread. The PR maintains the same functionality while reducing resource usage and complexity.

Note: This doesn't yet implement the recompilation on Forc.toml changes as mentioned in issue #7103, but adds a TODO placeholder for that functionality.

This PR is a precursor to #7139

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 #7147 will not alter performance

_{Comparing josh/didChangeWatchedFiles (8599f19) with master (1c885cf)}

Summary

✅ 22 untouched benchmarks

[IGI-111]

Always nice to see a PR with net negative line count!