(core) Forms post-release fixes and improvements

Summary:
Fixes misc. bugs with forms, updates Grist URLs on static form pages to link
to the new forms marketing page, and adds a forms announcement popup that's
shown next to the Add New button within a document.

Test Plan: Browser tests.

Reviewers: jarek

Reviewed By: jarek

Differential Revision: https://phab.getgrist.com/D4185

app/client/models/DocPageModel.ts

@@ -221,6 +221,11 @@ export class DocPageModelImpl extends Disposable implements DocPageModel {
             // "Add New" menu should have the same width as the "Add New" button that opens it.
             stretchToSelector: `.${cssAddNewButton.className}`
           }),
+          activeDoc.behavioralPromptsManager.attachPopup('formsAreHere', {
+            popupOptions: {
+              placement: 'right',
+            },
+          }),
           testId('dp-add-new'),
           dom.cls('tour-add-new'),
         ),

app/client/models/HomeModel.ts

@@ -158,7 +158,7 @@ export class HomeModelImpl extends Disposable implements HomeModel, ViewSettings
     wss.every((ws) => ws.isSupportWorkspace || ws.docs.length === 0)));
 
   public readonly shouldShowAddNewTip = Observable.create(this,
-    !this._app.behavioralPromptsManager.hasSeenTip('addNew'));
+    !this._app.behavioralPromptsManager.hasSeenPopup('addNew'));
 
   private _userOrgPrefs = Observable.create<UserOrgPrefs|undefined>(this, this._app.currentOrg?.userOrgPrefs);