gd: Add module started query method

Bug: 182544206
Test: gd/cert/run
Tag: #refactor
BYPASS_LONG_LINES_REASON: Bluetooth likes 120 lines

Change-Id: I7d2dedd4aaa20fd6811166c86d1b9931e6dda536
diff --git a/system/gd/stack_manager.h b/system/gd/stack_manager.h
index 5a9fa28..985bd0b 100644
--- a/system/gd/stack_manager.h
+++ b/system/gd/stack_manager.h
@@ -32,6 +32,11 @@
     return static_cast<T*>(registry_.Get(&T::Factory));
   }
 
+  template <class T>
+  bool IsStarted() const {
+    return registry_.IsStarted(&T::Factory);
+  }
+
  private:
   os::Thread* management_thread_ = nullptr;
   os::Handler* handler_ = nullptr;