Reenable node name case setting + code cleanups

The method _generate_serial_child_name is indeed called relatively often
in editor mode, but that commented out code chunk hardly adds to its
slowness (and with the default setting, not at all).

Also did various related code cleanups and simplifications.

tools/editor/plugins/spatial_editor_plugin.h

@@ -156,13 +156,11 @@ private:
 		NAVIGATION_MAYA,
 		NAVIGATION_MODO,
 	};
-	NavigationScheme _get_navigation_schema(const String& p_property);
 
 	enum NavigationZoomStyle {
 		NAVIGATION_ZOOM_VERTICAL,
 		NAVIGATION_ZOOM_HORIZONTAL
 	};
-	NavigationZoomStyle _get_navigation_zoom_style(const String& p_property);
 
 	enum NavigationMode {
 		NAVIGATION_NONE,