Use the expressive MotionScheme in PlatformTheme

This CL makes PlatformTheme use the expressive MotionScheme everywhere.
The expressive theme is meant to be used for the new M3, and given that
MotionScheme is almost not used anywhere yet apart from STL and the
Motion Mechanics libraries, I think that this is a good and safe change
to do now. This should make our animations slightly bouncy and more
delightful.

Bug: 417444347
Test: Manual, observed slightly bouncier animations
Flag: com.android.systemui.scene_container
Change-Id: I8f986b7b8693986e2a36c3510bab9f56a901ac17