Pausing app surface to receive touch during predictive back animation.

App can trigger an unexpected transition due to receive touch event
on it's surface, core isn't able to detect what could happen from that
touch and thus unable to polish the transition. So before app's
onBackInvoked callback being called, disallow the app from receive
touch event, until the close transition is ready.

Bug: 308395772
Test: tried on cross-activity/cross-task/back-to-home animation that
the touch event on animation targets during animation will be ignored.
Test: verify won't affect multiple gesture ag/25007350.

Change-Id: Icbd099d8ea90e9ba3e300c8c297961e1cd518245