Set the footer actions visibility outside of the ViewModel (1/2)

This CL removes FooterActionsViewModel.isVisible and sets the footer
actions view visibility directly in QsImpl, like most other QS views.
This avoids flickers caused by delayed collection of the previous
isVisible flow.

Bug: 302118830
Test: Manual, using steps from b/302118830#comment1
Change-Id: I4b678427eeb59de279703025f2fd3c78720dac9f