Log proc_id's pid when available (#1904)

Summary:
Pull Request resolved: #1904

It is useful to know which pid this proc is running on. In the long run, we probably should use hyper cli to get this info, but a log should be also good as a quick workaround.

Reviewed By: mariusae

Differential Revision: D87112445

fbshipit-source-id: d0c2a7c92b8234dcdecddffd34270a90c6e4785f

Author: pzhan9

hyperactor_mesh/src/bootstrap.rs

@@ -933,6 +933,7 @@ impl BootstrapProcHandle {
         addr: ChannelAddr,
         agent: ActorRef<ProcMeshAgent>,
     ) -> bool {
+        tracing::info!(proc_id = %self.proc_id, %addr, "{} running on pid {}", self.proc_id, pid);
         self.transition(|st| match st {
             ProcStatus::Starting | ProcStatus::Running { .. } => {
                 *st = ProcStatus::Ready {