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/manager.ts

@@ -6,6 +6,7 @@ import {DecoratorListener} from "lexical/LexicalEditor";
 import type {NodeKey} from "lexical/LexicalNode";
 import {EditorContextToolbar, EditorContextToolbarDefinition} from "./toolbars";
 import {getLastSelection, setLastSelection} from "../../utils/selection";
+import {DropDownManager} from "./helpers/dropdowns";
 
 export type SelectionChangeHandler = (selection: BaseSelection|null) => void;
 
@@ -21,6 +22,8 @@ export class EditorUIManager {
     protected activeContextToolbars: EditorContextToolbar[] = [];
     protected selectionChangeHandlers: Set<SelectionChangeHandler> = new Set();
 
+    public dropdowns: DropDownManager = new DropDownManager();
+
     setContext(context: EditorUiContext) {
         this.context = context;
         this.setupEventListeners(context);