Revert "Revert "ART: Start RuntimeCallbacks""

This reverts commit bf6331a45f730e1f1044af2ce43bceda660ae6fc.

Switch to using the mutator lock.

Bug: 31684920
Test: m test-art-host-gtest-runtime_callbacks_test
Test: art/tools/run-jdwp-tests.sh --mode=host --debug
Change-Id: I6ce0f71de2aa9f90cd23cfca7723a793b560b16b
diff --git a/runtime/thread.h b/runtime/thread.h
index 2b451bc..166ed21 100644
--- a/runtime/thread.h
+++ b/runtime/thread.h
@@ -1704,6 +1704,14 @@
   Thread* const self_;
 };
 
+class ThreadLifecycleCallback {
+ public:
+  virtual ~ThreadLifecycleCallback() {}
+
+  virtual void ThreadStart(Thread* self) REQUIRES_SHARED(Locks::mutator_lock_) = 0;
+  virtual void ThreadDeath(Thread* self) REQUIRES_SHARED(Locks::mutator_lock_) = 0;
+};
+
 std::ostream& operator<<(std::ostream& os, const Thread& thread);
 std::ostream& operator<<(std::ostream& os, const StackedShadowFrameType& thread);