Use IBooleanResultCallback when appropriate in IInputContext

This is a small code clean up in IInputContext, which should have no
observable behavior change for app/IME developers.

In the following two methods we have used IIntResultCallback to return
a boolean value in a synchronous manner by using 0 to represent false
and 1 to represent true.

 * IInputContext#requestCursorUpdates
 * IInputContext#commitContent

Now that we have IBooleanResultCallback, we can just use true and
false without any conversion.

Bug: 192412909
Test: presubmit
Change-Id: Id6beaf3c9350b70138eb77f406be86fe2c8b679f