Don't let IME move to recents activity during recents transition

In shell transitions, recents opens on top, but in transient mode
(meaning it doesn't cause the other apps to pause). This means the
other apps should be running un-interrupted. This includes not
taking the IME away.

To handle this, adjust the IME logic so that transient-launching
activities are NOT canBeImeTarget.

Also fix a bug in isVisibleOrAdding where it was using
visibleRequested instead of visible (if you look at the change
history, !hiddenRequested was incorrectly replaced by
visibleRequested instead of visible).

Also fix a bug where a defer/continue of updateImeTarget was
updating the target even when an update was never requested while
it was deferred. This was causing it to be called prematurely
during activitystarter (where global lock is held).

Bug: 193565597
Test: atest ReOpenImeWindowTest SwitchImeWindowsFromGestureNavTest
Change-Id: Ic537d77c8b0e10e80444dd46d7b49e5a9bd63d6c