Use customized back-invoked-callback when intercepting back

The back navigation is intercepted when performing a back gesture
while Bubble expanded. Although the back preview animation is dropped
dropped in this case, it still gets the back-invoked-callback from
the client, which will still invoke Activity#onBackPressed by default
(via dispatch back key event in ViewRootImpl) when the back gesture
completed. Activity finishes itself when #onBackPressed is called.
So the bubble is removed vs. collapsed.

Therefore, here uses a customized back-invoked-callback when intercept
happens and avoid sending back key event to the client.

Bug: 427336494
Test: swipe back when bubble expanded
Test: BackNavigationControllerTests
Flag: EXEMPT bugfix
Change-Id: I20e5f6593c877af787d203436af8486ede3219f0