[UITests] Add features for running tests in better isolation and for handling Multiple Test Cases

[PureWeen]

Description

• We need the ability better isolation the main page, like we had in compatibility tests, for most tests that are testing Page types (especially shell)
• Try doing this with new window (need to test iOS) not sure if this will work for iOS

FlyoutNavigationBetweenItemsWithNavigationStacks is a good candidate for validating this scenario.

• Add the ability to handle multiple testcases
  • In Compatibility we would swap out the main page between each test case. We don't need to go as full on with these new UITests but we need a way to clean the surface and run multiple test cases.
  • CollectionViewTests are a good candidate for validating this scenario

We've added this issue to our backlog, and we will work to address it as time and resources allow. If you have any additional information or questions about this issue, please leave a comment. For additional info about issue management, please read our Triage Process.