[Provider Model] Update Airplane mode message

- Show Airplane mode message when Airplane mode is enabled

- Show the same message whether Wi-Fi is enabled or disabled

- Screenshot:
  https://screenshot.googleplex.com/9FgqG7WWskRLZxo
  https://screenshot.googleplex.com/4g4kvnAT6aYN57s

Bug: 181858434
Test: manual test
make RunSettingsRoboTests ROBOTEST_FILTER=NetworkProviderSettingsTest

Change-Id: I3cb5a8bc7cb4d1e8678eb6d75116effd00ac9432