Consuming common key combinations in app priority

Some apps or games could use the combo keys such as holding Ctrl or Alt
to trigger its own shortcut or behavior. To prevent the system shortcut
might be handled before dispatching to the app, we move these keys
handling to 'dispatchUnhandledKey' when the app didn't handle.

This will also fix the corresponding state when the modifier key is
released.

Bug: 156619364
Bug: 213096704
Test: atest AppKeyCombinationsTest
Change-Id: I42770045c61ad6396b27132b8a61d34fc121d77e