Wrap Activity->Activity changes in non-activity transitions

When an Activity->Activity transition gets combined into a
non-activity transition, the anim-root no-longer properly
crops the activities and the activities also aren't offset
properly.

This fixes the offset by calculating offset from anim-root
instead of using endRelOffset (which is relative to the
true parent surface). Then, if it detects activity change
in non-activity task, it will create a wrapper surface.

Bug: 322113725
Test: use a test-app or otherwise have an activity->activity
      change happen at same time as translucent task closes.
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:163d0a7c6fd7a2d63d08181832ce8f80a74dde13)
Merged-In: I5e6c083e9c9f8c82ec8ffe6828d607fc019aeb59
Change-Id: I5e6c083e9c9f8c82ec8ffe6828d607fc019aeb59