(core) Restoring cursor position on raw data views

Summary:
This diff introduces cursor features for raw data views:
- Restoring cursor position when the browser window is reloaded
- Restoring the last edit position when the browser window is reloaded

Test Plan: Added tests

Reviewers: alexmojaki

Reviewed By: alexmojaki

Subscribers: jarek

Differential Revision: https://phab.getgrist.com/D3314

app/client/components/BaseView.js

@@ -236,6 +236,9 @@ BaseView.commonCommands = {
  * loading.
  */
 BaseView.prototype.setCursorPos = function(cursorPos) {
+  if (this.isDisposed()) {
+    return;
+  }
   if (!this._isLoading.peek()) {
     this.cursor.setCursorPos(cursorPos);
   } else {