Lexical: Updated dropdown handling to match tinymce behaviour

Now toolbars stay open on mouse-out, and close on other toolbar open,
outside click or an accepted action.
To support:
- Added new system to track and manage open dropdowns.
- Added way for buttons to optionally emit events upon actions.
- Added way to listen for events.
- Used the above to control when dropdowns should hide on action, since
  some dont (like overflow containers and split dropdown buttons).

resources/js/wysiwyg/ui/framework/blocks/overflow-container.ts

@@ -19,6 +19,7 @@ export class EditorOverflowContainer extends EditorContainerUiElement {
                 label: 'More',
                 icon: moreHorizontal,
             },
+            hideOnAction: false,
         }, []);
         this.addChildren(this.overflowButton);
     }