lsp: Watch paths outside of worktrees at language servers request (#17499)

Another stab at https://github.com/zed-industries/zed/pull/17173, this
time fixing the segfault found in
https://github.com/zed-industries/zed/pull/17206

Release Notes:

- Improved language server reliability in multi-worktree projects and
monorepo. We now notify the language server more reliably about which
files have changed.

crates/snippet_provider/src/lib.rs

@@ -169,7 +169,12 @@ impl SnippetProvider {
 
             let (mut entries, _) = watcher.await;
             while let Some(entries) = entries.next().await {
-                process_updates(this.clone(), entries, cx.clone()).await?;
+                process_updates(
+                    this.clone(),
+                    entries.into_iter().map(|event| event.path).collect(),
+                    cx.clone(),
+                )
+                .await?;
             }
             Ok(())
         })