8307517: Add VMErrorCallback infrastructure to extend hs_err dumping

Reviewed-by: eosterlund, aboldtch, dholmes, stuefe

src/hotspot/share/runtime/thread.cpp

@@ -98,6 +98,7 @@ Thread::Thread() {
   _jvmti_env_iteration_count = 0;
   set_allocated_bytes(0);
   _current_pending_raw_monitor = nullptr;
+  _vm_error_callbacks = nullptr;
 
   // thread-specific hashCode stream generator state - Marsaglia shift-xor form
   _hashStateX = os::random();