[Provider model] Add "Turn off/on Wi-Fi" link to Internet Panel

- Replace the left menu button with "Turn off/on Wi-Fi"
  - Remove the TurnOnWifiSlice

- Show "Wi-Fi is off" sub-title when Wi-Fi is disabled
  - Remove the "Wi\u-Fi is turned on" sub-title when APM is on.

Bug: 188710392
Test: manual test
atest -c InternetConnectivityPanelTest
make RunSettingsRoboTests ROBOTEST_FILTER=com.android.settings.panel

Change-Id: I53e200f6cadf8b712bf794bcbd5ff79f0f239cc0