fix: ensure the inspector agent is shutdown before cleaning up the node env (#18028)

* fix: ensure the inspector agent is shutdown before cleaning up the node env

* spec: add tests to ensure clean shutdown with connected inspector agent

* Update node_debugger.cc

atom/browser/node_debugger.h

@@ -20,6 +20,7 @@ class NodeDebugger {
   ~NodeDebugger();
 
   void Start();
+  void Stop();
 
  private:
   node::Environment* env_;