Allow custom animations for AE change transitions behind a flag.

This change also checks for change transition animations for zero duration, which will now fallback to jump cut. Open/close transition animations already fallback to jump cut when there is an animation specified with no duration.

Bug: 293658614
Demo: https://screencast.googleplex.com/cast/NDU3Nzk5MjQzMTg5NDUyOHxjNjZlODgxMy0xMg
Test: atest ActivityEmbeddingAnimationRunnerTests
Test: Manual - Tested by hardcoding
TaskFragmentAnimationParams.setChangeAnimationResId with a custom
animation. This can later be passed in via Extensions API.
Flag: com.android.window.flags.activity_embedding_animation_customization_flag

Change-Id: Ide3ef1d8bb1800953dc0661219bf31152945f9e0