(core) Polish tutorial popups

Summary:
Includes the following changes:
 *  Adds "Click to expand" hover tooltip to all images
 *  Adds support for minimize/maximize by double clicking tutorial popup header
 *  Add New menu (and all other popups) should now persist when user moves tutorial popup
 *  Preserves scrollbar position when minimizing and maximizing tutorial popup
 *  Formula cell editor (and other elements) should now be stacked under tutorial

Test Plan: Browser and manual tests.

Reviewers: jarek

Reviewed By: jarek

Differential Revision: https://phab.getgrist.com/D3864

app/client/models/DocPageModel.ts

@@ -262,15 +262,17 @@ export class DocPageModelImpl extends Disposable implements DocPageModel {
       t("Error accessing document"),
       t("Reload"),
       async () => window.location.reload(true),
-      isDocOwner
-        ? t("You can try reloading the document, or using recovery mode. " +
-            "Recovery mode opens the document to be fully accessible to " +
-            "owners, and inaccessible to others. It also disables " +
-            "formulas. [{{error}}]", {error: err.message})
-        : isDenied
-          ? t('Sorry, access to this document has been denied. [{{error}}]', {error: err.message})
-          : t("Document owners can attempt to recover the document. [{{error}}]", {error: err.message}),
       {
+        explanation: (
+          isDocOwner
+            ? t("You can try reloading the document, or using recovery mode. " +
+                "Recovery mode opens the document to be fully accessible to " +
+                "owners, and inaccessible to others. It also disables " +
+                "formulas. [{{error}}]", {error: err.message})
+            : isDenied
+              ? t('Sorry, access to this document has been denied. [{{error}}]', {error: err.message})
+              : t("Document owners can attempt to recover the document. [{{error}}]", {error: err.message})
+        ),
         hideCancel: true,
         extraButtons: !(isDocOwner && !isDenied) ? null : bigBasicButton(
           t("Enter recovery mode"),