[Wi-Fi] Replace WifiTracker with WifiTracker2 for SavedAccessPointsWifiSettings2

Use SavedNetworkTracker instead of WifiTracker, it provides Wi-Fi signal information
for saved networks. This is the main UX difference of this change.

Bug: 144543677
Test: make RunSettingsRoboTests ROBOTEST_FILTER=com.android.settings.wifi.
Change-Id: I546ad08ffd2f6f736023cb1f3e1cb344a5842e14
6 files changed