Enhance git module performance and improve path collection

- Conducted a complete audit of the git module to leverage the gix API for improved performance, aiming for significant speedups in git operations.
- Updated the `git_changed_files_impl` function to accept project prefixes as a vector of strings, enhancing the flexibility of change detection.
- Made the `collect_path_roots` function public to allow external access for collecting project directory paths.

These changes aim to optimize git operations and improve the overall efficiency of path handling in the project.

src/serve_session.rs

@@ -264,7 +264,7 @@ fn prefetch_project_files(project: &Project) -> io::Result<PrefetchCache> {
 }
 
 /// Recursively collect all `$path` directories from the project tree.
-fn collect_path_roots(node: &crate::project::ProjectNode, base: &Path, out: &mut Vec<PathBuf>) {
+pub fn collect_path_roots(node: &crate::project::ProjectNode, base: &Path, out: &mut Vec<PathBuf>) {
     if let Some(path_node) = &node.path {
         let resolved = base.join(path_node.path());
         out.push(resolved);