Do not set alpha for rotation enter animation

If alpha < 1 is set on display layer, all visible children layers
are also affected, which may look flickering because the layer
which occludes other layers becomes translucent.

Also add clip effects to reduce the high contrast between overlapped
and non-overlapped area of enter/exit animations. The long side will
shrink to short side, and vise versa.

Bug: 438615184
Flag: com.android.window.flags.no_alpha_rotation_enter_animation
Test: Expand notification shade, rotate device.
      The app content should not flash behind.
Test: Yellow color should not flash when rotating a sample app with
      surfaceView.setZOrderOnTop(true);
      surfaceView.setBackgroundColor(Color.YELLOW);
        surfaceCreated() {
          Surface surface = holder.getSurface();
          Canvas c = surface.lockCanvas(null);
          c.drawColor(Color.GRAY);
          surface.unlockCanvasAndPost(c);
        }

Change-Id: I66e73592695febfdef02b856ebd742e1a8a51b07