Add onPayloadFinished callback

onPayloadFinished will be called from the VM when the payload has just
finished.

Bug: 195381416
Test: atest MicrodroidHostTestCases
Change-Id: I9bb68c2192ee19a40634d10ba77af9d4c3ec30d0
diff --git a/vm/src/run.rs b/vm/src/run.rs
index 3b34bac..825fdeb 100644
--- a/vm/src/run.rs
+++ b/vm/src/run.rs
@@ -189,6 +189,10 @@
         Ok(())
     }
 
+    fn onPayloadFinished(&self, _cid: i32, _exit_code: i32) -> BinderResult<()> {
+        Ok(())
+    }
+
     fn onDied(&self, _cid: i32) -> BinderResult<()> {
         // No need to explicitly report the event to the user (e.g. via println!) because this
         // callback is registered only when the vm tool is invoked as interactive mode (e.g. not