BHV-10909: Header/Input: 'Dismiss On Enter' does not Dismiss but Reloads VKB

### Issue:
moon.Input instructs Spotlight to ignore enter key events, and then handles key up events to remove focus when dismissOnEnter is true, and the keyCode is an enter key. When selection logic was moved from spotlightKeyDown to spotlightKeyUp, this caused problems with the dismissOnEnter feature of moon.Input, because the enter keyDown event was being ignored, but the enter keyUp was not, because by the time OnSpotlightKeyUp executes, input no longer has the focus.
### Fix:
Add a bool _bLastKeyDownIgnored, and then check to see the selection logic is not performed if _bLastKeyDownIgnored is true.