autofill: ViewRootImpl.dispatchKeyFromIme() should not be dropped

ag/3628400 bypass unhandled keyevent from autofill to app window,
that solves the issue of using physical keyboard. But we still have
issue When user uses touch screen with IME.

There are two ways that IME interacts with app:
1. IME directly replaces text of TextView. (Sample app login screen)
2. IME calls ViewRootImpl.dispatchKeyFromIme. (Sample app credit card
   screen)

In the second case, because we gave focus to autofill window,
ViewRootImpl will drop the event.

The fix checks if autofill window is showing fillui it should not
drop event. And dispatchKeyFromAutofill can use the same check, no
longer need FLAG_FROM_AUTOFILL.

Bug: 74527545
Test: Manually check with login and credit card example, using IME
touchscreen and "adb shell input keyevent". I am not able to write
cts test without a fake IME

Change-Id: I698423d83ee8f9151d03a39b49e85416f7d6b615