Send telemetry events for pnpm usage (#13748)

This PR adds telemetry events for pnpm usage, similar to what we did for
Yarn in #12785.

Seems like useful information to have.

Release Notes:

- N/A

crates/client/src/telemetry.rs

@@ -202,6 +202,10 @@ impl Telemetry {
             event_coalescer: EventCoalescer::new(clock.clone()),
             max_queue_size: MAX_QUEUE_LEN,
             worktree_id_map: WorktreeIdMap(HashMap::from_iter([
+                (
+                    "pnpm-lock.yaml".to_string(),
+                    ProjectCache::new("pnpm".to_string()),
+                ),
                 (
                     "yarn.lock".to_string(),
                     ProjectCache::new("yarn".to_string()),