lsp: Treat unrooted paths as relative to the worktree root (#17769)

gopls would send us watch patterns like `**/*.mod` and we'd fall back to
watching `/`.

Release Notes:
- Fix file watching for go projects resorting to watching the fs root.

Co-authored-by: Thorsten <thorsten@zed.dev>

crates/project/src/lsp_store.rs

@@ -3499,7 +3499,7 @@ impl LspStore {
                                             .to_owned();
                                         let path = if Path::new(path).components().next().is_none()
                                         {
-                                            Arc::from(Path::new("/"))
+                                            Arc::from(Path::new(worktree_root_path))
                                         } else {
                                             PathBuf::from(path).into()
                                         };