Keyboard Manager UI needs Win App Driver tests

[arjunbalgovind]

Unit tests for the UI logic for validating shortcut and key selections was added in #5718, however these tests only cover the scenarios of a single drop down changing. In order to test more complex interactions where an error while changing one drop down results in multiple warnings and multiple drop downs getting modified requires the use of Win App driver tests.
Win app driver tests will also allow us to test adding/removing rows in the UI.