Move SceneTransitionLayout to a separate library (1/2)

This CL is a pure move that moves the code for SceneTransitionLayout
inside a separate library, so that it can be easily copied and reused as
part of the AndroidX benchmarks.

Bug: 300622679
Test: atest PlatformComposeSceneTransitionLayoutTests
Change-Id: I97cbe4515b1bc28db59c9f1234df823d727bc882
diff --git a/packages/SystemUI/Android.bp b/packages/SystemUI/Android.bp
index e40fcb2..a9673cc 100644
--- a/packages/SystemUI/Android.bp
+++ b/packages/SystemUI/Android.bp
@@ -61,6 +61,7 @@
             // Copied from compose/features/Android.bp.
             static_libs: [
                 "PlatformComposeCore",
+                "PlatformComposeSceneTransitionLayout",
 
                 "androidx.compose.runtime_runtime",
                 "androidx.compose.material3_material3",