Make IInputMethodManager to oneway (3/N)

-. Create InputBindResult result callback and apply it
   to startInputOrWindowGainedFocus().
-. Create a callback utility class.

Bug: 163453493
Test: Manual test with keyboard
Test: atest CtsInputMethodTestCases
Change-Id: If4b40244a2e0e3b11c38c1da9340ba8e5166ad64