Finish InputInjection Work + Fluent API Helper

[michael-hawker]

Following on from #124 and #161, we're waiting for 1.1.2 of WinAppSDK or beyond to make progress on this front due to blocking issues with CI and MSTest Discovery. (Also see https://github.com/MicrosoftDocs/windows-uwp/issues/3887)

Once those are resolved in the WinAppSDK we can resume investigating our InputInjection approach which appears to work (at least for mouse click) without issue on UWP.

• [ ] Investigate helper methods for more 'ui testing' scenarios
  • [x] Since we own the apps and their deployment can we use more restricted capabilities like the InputInjection rescap? And does that work in WinUI 3 as well?
  • [ ] Does this work in the CI?
  • [x] UWP
  • [ ] WinUI 3
• [ ] Use GridSplitter as a test case and see if we can:
  • [ ] Test Localization (will be good test for UWP/WinUI 3 and resource loading)
  • [ ] Test a mouse drag (if we get injector working) replicate the UI Test we had for GridSplitter
• [ ] Add Fluent API helper methods

From original thread comment:

Thanks @Sergio0694, yeah I was roughly thinking something like:

await SimulateInput.StartTouch()
                   .MouseDown(coord)
                   .MouseMove(cx, cy, seconds: 0.5, points: 10)
                   .MouseUp()
                   .Execute();

As we need to preface and end the operation with initializing/uninitializing the touch injector code, as well as generate/use a unique pointer id across the instructions (and if we want to use relative positioning between operations keep track of the initial point).

Anyway, bit more investigation to do, as not sure if this is going to run in the CI yet (though even then may have value).

Originally posted by @michael-hawker in https://github.com/CommunityToolkit/Labs-Windows/issues/124#issuecomment-1157848762

Current work in llama/input-injection-test branch.

[michael-hawker]

Good test cases for Keyboard driven scenarios would be the TokenizingTextBox:

1. test clearing an inner text box and the text changing
2. overwriting an existing token and typing a character and ensuring that's set in the textboxes (text and inner box)

See https://github.com/CommunityToolkit/WindowsCommunityToolkit/issues/4749#issuecomment-1281611691