Hide brightness slider on external displays

Right now there is no way control the brightness of external displays. This removes the slider from the compose QS fragment if it is being displayed on an external display.

Bug: 362719719
Bug: 397156848
Test: QSFragmentComposeViewModelTest
Flag: com.android.systemui.shade_window_goes_around
Change-Id: I34572262912ceb05e2dd4a2dc0626c0f44e5848d