Extract editor run toolbar into its own component

- Simplify and update its logic.
- Simplify EditorScript.
- Improve EditorNode and other relevant includes.
- Fix scene-based path in the movie writer when
reloading a scene.

editor/editor_run.h

@@ -50,6 +50,7 @@ private:
 public:
 	Status get_status() const;
 	String get_running_scene() const;
+
 	Error run(const String &p_scene, const String &p_write_movie = "");
 	void run_native_notify() { status = STATUS_PLAY; }
 	void stop();