InternetPreferenceController V2 (1/n)

Refactor the InternetPreferenceController, migrate to repository and
flow, run data loading on background thread.

Only add Wifi summary for now.

Bug: 339884322
Flag: com.android.settings.flags.internet_preference_controller_v2
Test: manual - on Internet
Test: unit test
Change-Id: Ibd8911bc11b24d4a7e2ef320dea4d38b9c3a864f