Fix color filling on some Wifi pages

Since there's no edge-to-edge in the theme that Wifi page applied, it
caused the different colors filled in status bar and collapsing
toolbar area separately. It can be fixed by updating the theme to
Theme.SubSettings.

Fix: 187016196
Fix: 187021412
Test: visual verified
Change-Id: I686861c37acfb1eeddda1278cd70fa5bfd44cc1d