[Wi-Fi] Replace WifiTracker with WifiTracker2 in WifiDetailPreferenceController2

There are still many methods not implemented in WifiEntry. This change has below workarounds:

1. Add WifiEntryShell to provide dummy WifiEntry methods.
2. Add @Ignore to WifiDetailPreferenceController2Test.

Must remove these workarounds after we have more constructed WifiEntry methods.

Bug: 143326832
Test: make RunSettingsRoboTests ROBOTEST_FILTER=com.android.settings.wifi.details2
      make RunSettingsRoboTests ROBOTEST_FILTER=com.android.settings.wifi.savedaccesspoints2
      make RunSettingsRoboTests ROBOTEST_FILTER=com.android.settings.wifi
Change-Id: Ic2edb424b9c645838558fe131991ccb9105dc64c