Allow setting open/close/change animations for ActivityEmbedding (AE) from...

Allow setting open/close/change animations for ActivityEmbedding (AE) from SplitAttributes behind a flag.

Additionally:
- Fix bug in TaskFragmentAnimationParams#hasOverrideAnimation.
- Check for default AnimationParams values in WindowExtensionsTest.
- (Flagged) Return early in ActivityEmbeddingAnimationRunner#createOpenCloseAnimationAdapters if a jump cut is expected.
- (Flagged) Explicitly create custom animation for AE change transitions with TRANSIT_CHANGE mode. (Some change transitions come bundled with other modes, so we want to find the custom animation specifically for change.)
- (Flagged) Enforce only loading AE custom animations by resource Id from the default "android" package.

Bug: 293658614
Test: Manually tested end-to-end via demo app with Extensions build and Jetpack API changes patched
Test: atest WMJetpackUnitTests:WindowExtensionsTest
Flag: com.android.window.flags.activity_embedding_animation_customization_flag
Change-Id: I7a3e55304e593bc42f1443be848c6d673de968ad