Bug 1887594 - Fix saveTabToExistingCollectionFromMainMenuTest UI test r=aaronmt

Bug 1887594 - Fix saveTabToExistingCollectionFromMainMenuTest UI test r=aaronmt

- The inconsistencies were caused by the fact that the tabs weren't properly selected when trying to create a collection.
- To overcome this problem, I've added a retry loop to the the tab selection function and also added an extra assertion (**verifyTabsMultiSelectionCounter**()) inside the **selectTab** function which will help us identify more easily if there is a tab selection problem

- This patch should fix the following intermittent UI tests affected by the above mentioned problem:
  -  saveTabToExistingCollectionFromMainMenuTest
  -  renameCollectionTest
  -  verifyExpandedCollectionItemsTest
  -  removeTabFromCollectionUsingSwipeRightActionTest
  -  removeTabFromCollectionUsingSwipeLeftActionTest
  -  saveTabToExistingCollectionUsingTheAddTabButtonTest

✅ saveTabToExistingCollectionFromMainMenuTest - successfully passed 150x on Firebase
✅ renameCollectionTest - successfully passed 150x on Firebase
✅ verifyExpandedCollectionItemsTest - successfully passed 150x on Firebase

Differential Revision: https://phabricator.services.mozilla.com/D207146