[SB Refactor] Migrate the wifi location-based VMs to use `by`.

This means that we don't need to update all the location-based VMs
whenever we want to add a new output flow (which we'll need to do when
we add wifi <--> mobile RAT spacing). And, it now matches the mobile
view model setup.

Bug: 238425913
Test: verify wifi icon still updates
Test: turn on icon debug coloring, verify icon is different color in
each of the three locations
Test: atest WifiViewModelTest WifiViewModelIconParameterizedTest
ModernStatusBarWifiViewTest WifiScreenshotTest

Change-Id: I91129d6142af648c32f95d8e8f681042941a5782