[Provider Model] Add Wi-Fi toggle

- Network & internet Settings
  - Remove “Show airplane mode networks"

- Internet Settings
  - Add “Wi-Fi” switch preference
    - Show “Find and connect to Wi-Fi networks” in summary

- Screenshot:
  https://screenshot.googleplex.com/AnoXf4qDe2jPirP

Bug: 181858434
Test: manual test
atest -c NetworkDashboardFragmentTest \
         WifiSwitchPreferenceControllerTest
make RunSettingsRoboTests ROBOTEST_FILTER=NetworkProviderSettingsTest

Change-Id: Ic420ff40cfdfb3ae29ee6f754ce139cb54651bda