Refactor back navigation animtion (1/2)

In previous design, it would create all necessary leashes when starting
back navigation, and they would be carried by `BackNavigationInfo` and
`BackEvent` and would finally deliver to the shell and animator side.

In this CL, we will use the adapter that wraps a back animation runner
to deliver all leashes in next surface placement after back navigation
has started.

In shell side, every animator should be registered by type, so the
adapter could deliver leashes via IRemoteAnimationRunner to the
target animator, and invoke callback when it finished.

This also eliminated all unecessary fields from `BackNavigationInfo` and
`BackEvent`.

Bug: 241808055
Test: atest BackNavigationControllerTests BackAnimationControllerTest
      BackNavigationTest
Change-Id: I8bbec0d8d9631110c3d2788d958b50ae487520a7