Make IME visiblity stable without unexpected hidden when setControl

2 reasons that may unexpectly calls hideMySoftInput from IME:

1) When requesting show IME on the activity, before receiving the
   control from server side, the null control might received from the
   relayoutWindow, if initially in consumer side didn't get the control
   yet, we should not hide the IME immediately to broke the on-going
   show request.

2) When ImeInsetsSourceConsumer#onWindowFocusGained, if we don't set
   mIsRequestedVisibleAwaitingControl as true if it has requested IME
   visible but not yet get control, it also could possble mistakenly
   hide IME when ImeInsetsSourceConsumer#setControl.

As the result, we should prevent both case with

1) add returned value for InsetsSourceConsumer#setControl to see whether
   the control has changed from the server, if the control didn't
   change like receiving a duplicated null control callback,
   then in ImeInsetsConsumer didn't have to do anything.
2) set mIsRequestedVisibleAwaitingControl as true when receiving
   onWindowFocusGained and the host is waiting the control to make
   IME visibility reliable.

Bug: 227142436
Bug: 204524304
Test: atest FlickerTests:LaunchAppShowImeAndDialogThemeAppTest
        --rerun-until-failure 10

Change-Id: If4b09f5b52bc96cf3429aaa912961f3ac4e326f2