Make IInputMethodPrivilegedOperations to async (4/N)

-. Remove VoidResultCallback of updateStatusIcon
   and let it be truly asynchronous.
-. Rename this method to updateStatusIconAsync.

Bug: 183587528
Test: atest CtsInputMethodTestCases
Change-Id: Ic7759354ec06a3293ea370ab7afe7422eb2d9356