Call onInputConnectionClosed synchronously

This ensures that, when switching focus from one view to another,
HandwritingInitiator will receive the onInputConnectionClosed callback
for the first view before receiving the onInputConnectionCreated for the
second view.

Bug: 275598091
Test: atest android.view.inputmethod.cts.StylusHandwritingTest
Change-Id: Ifafb9c3adbdd32a307de1ea65cc2d7384f4d8a71