Initial support for display rotation in shell transitions

This puts display-content as another WC in a transition. It then
adds WC rotation to change tracking. If there is a rotation,
the shell-side handlers will play the transition.

This replaces ScreenTransitionAnimation, seamless-rotation, and
fixed-rotation:

 ScreenTransitionAnimation implementation will move to shell.

 seamless-rotation is redundant because the rotation setup is
 intrinsically "seamless": it requires shell to imbue an
 animation onto it rather than just doing the jump-cut.

 fixed-rotation is now just a custom animation where we
 counter-rotate the closing app on frame 1 and then perform
 the normal open animation on the opening app.

Bug: 179270750
Test: DisplayContentTests#testShellTransitRotation
      enable shell transitions and rotate the device or launch
      and close apps in different orientations.
Change-Id: I4bc23b2e614ba85bf9752f62da4c3f8d0c90436d