Notif redesign: Update footer view layout

This CL updates the layout of the footer view (behind a flag) to match
the new specs. The new buttons don't do anything yet, but the clear all
button still works.

Bug: 375010573
Test: manually verify that the new design looks good and changes when
the theme changes
Flag: com.android.systemui.notifications_redesign_footer_view

Change-Id: Ib83cd37a1f5c2da80033f6f89ed8a52947c12a6b