Make IInputMethodPrivilegedOperations to async (5/N)

-. Remove VoidResultCallback of notifyUserAction.
   and let it be truly asynchronous.
-. Rename this method to notifyUserActionAsync.

Bug: 183587528
Test: atest CtsInputMethodTestCases
Change-Id: I384fd689b6bd1d418ff5208444fbba2c1eac6f85