Use ShadeWindowGoesAround helper class instead of just reading the flag

This also provides some methods to assert whether the flag is on or off.

Bug: 362719719
Bug: 374267505
Test: presubmits
Flag: com.android.systemui.shade_window_goes_around
Change-Id: I41dba24c2404835c7756b7fc0659fcd49cc8fdc6
4 files changed