Implement elapsed_time for VmBooted and VmExited

Bug: 243613715
Test: atest MicrodroidTestCase#testTelemetryPushedAtoms
Change-Id: I837c3c1606aa128663b703898c62ffb777938d44
diff --git a/virtualizationservice/src/aidl.rs b/virtualizationservice/src/aidl.rs
index 5f4b7a7..553ddb2 100644
--- a/virtualizationservice/src/aidl.rs
+++ b/virtualizationservice/src/aidl.rs
@@ -1046,7 +1046,8 @@
             let stream = vm.stream.lock().unwrap().take();
             vm.callbacks.notify_payload_started(cid, stream);
 
-            write_vm_booted_stats(vm.requester_uid as i32, &vm.name);
+            let vm_start_timestamp = vm.vm_start_timestamp.lock().unwrap();
+            write_vm_booted_stats(vm.requester_uid as i32, &vm.name, *vm_start_timestamp);
             Ok(())
         } else {
             error!("notifyPayloadStarted is called from an unknown CID {}", cid);