Add support for UIPickerViews in Subliminal

UIPickerViews are under a different Window other than keyWindow, so I had to find the other one.  Otherwise it is pretty straightforward.  I'm leaning on the UIA methods a bit more heavily for interacting with the element, but open to suggestions.

Added one fairly comprehensive test case.
The only thing it does is make the cursor not blink in the text box. Again, it was more just matching our use case, but it probably doesn't make any difference to the actual test itself. Happy to pull it out or just comment it as desired.