Introduce SceneTransitionLayout (1/2)

This CL introduces the first version of SceneTransitionLayout, which is
meant to be first used by Flexiglass for the main SystemUI scene
transitions. See http://go/sysui-compose-transitions for more details
and http://ag/24006325 for an example.

To review this CL, I suggest to first look at the public APIs in:
 - SceneTransitionLayout.kt
 - SceneTransitionLayoutState.kt
 - TransitionDsl.kt

Then, review the implementation (in order):
 - SceneTransitionLayoutImpl.kt
 - AnimateToScene.kt
 - Scene.kt
 - Transformation.kt (and a simple example like Translate.kt)
 - Element.kt
 - SwipeToScene.kt
 - AnimateSharedAsState.kt
 - Everything else

Bug: 290184746
Test: atest PlatformComposeCoreTests
Change-Id: I6b48e27817bd86a6898624bfe226076ee70027a8