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/export/editor_export_platform.cpp

@@ -42,6 +42,7 @@
 #include "editor/editor_paths.h"
 #include "editor/editor_scale.h"
 #include "editor/editor_settings.h"
+#include "editor/export/editor_export.h"
 #include "editor/plugins/script_editor_plugin.h"
 #include "editor_export_plugin.h"
 #include "scene/resources/packed_scene.h"