refactor: migrate account-menu to react - implement functionality

- remove all Angular code related to `account-menu`
- rename React component to AccountMenu so that many parts of old code remain unchanged
- code cleanup

app/assets/javascripts/ui_models/app_state/account_menu_react_state.ts

@@ -1,33 +0,0 @@
-import { action, makeObservable, observable } from "mobx";
-import { WebApplication } from '@/ui_models/application';
-
-export class AccountMenuStateReact {
-  show = false;
-  signingOut = false;
-
-  constructor(
-    // private application: WebApplication,
-    // appEventListeners: (() => void)[]
-  ) {
-    makeObservable(this, {
-      show: observable,
-      signingOut: observable,
-
-      setShow: action,
-      toggleShow: action,
-      setSigningOut: action,
-    });
-  }
-
-  setShow = (show: boolean): void => {
-    this.show = show;
-  }
-
-  setSigningOut = (signingOut: boolean): void => {
-    this.signingOut = signingOut;
-  }
-
-  toggleShow = (): void => {
-    this.show = !this.show;
-  }
-}

app/assets/javascripts/ui_models/app_state/app_state.ts

@@ -14,14 +14,13 @@ import { Editor } from '@/ui_models/editor';
 import { action, makeObservable, observable } from 'mobx';
 import { Bridge } from '@/services/bridge';
 import { storage, StorageKey } from '@/services/localStorage';
-import { AccountMenuState } from './account_menu_state';
 import { ActionsMenuState } from './actions_menu_state';
 import { NoAccountWarningState } from './no_account_warning_state';
 import { SyncState } from './sync_state';
 import { SearchOptionsState } from './search_options_state';
 import { NotesState } from './notes_state';
 import { TagsState } from './tags_state';
-import { AccountMenuStateReact } from '@/ui_models/app_state/account_menu_react_state';
+import { AccountMenuState } from '@/ui_models/app_state/account_menu_state';
 
 export enum AppStateEvent {
   TagChanged,
@@ -61,8 +60,7 @@ export class AppState {
   onVisibilityChange: any;
   selectedTag?: SNTag;
   showBetaWarning: boolean;
-  readonly accountMenu = new AccountMenuState();
-  readonly accountMenuReact: AccountMenuStateReact;
+  readonly accountMenu: AccountMenuState;
   readonly actionsMenu = new ActionsMenuState();
   readonly noAccountWarning: NoAccountWarningState;
   readonly sync = new SyncState();
@@ -98,7 +96,7 @@ export class AppState {
       application,
       this.appEventObserverRemovers
     );
-    this.accountMenuReact = new AccountMenuStateReact();
+    this.accountMenu = new AccountMenuState();
     this.searchOptions = new SearchOptionsState(
       application,
       this.appEventObserverRemovers