Allow User switcher dialog to open on external displays

This uses the context from  ShadeDialogContextRepository when opening a user switcher dialog from QS footer.

The context is not passed from KeyguardQsUserSwitchController anymore, as that one would be wrong (as it's a WindowContext for TYPE_NOTIFICATION_SHADE, that doesn't accept

Bug: 362719719
Bug: 383294128
Test: UserSwitchDialogControllerTest, UserSwitchDialogControllerTest
Flag: com.android.systemui.shade_window_goes_around
Change-Id: Ic0a028b216f3fbf41e6b9a762c335c0574c054f9