[Provider Model] Internet Panel - Airplane mode is on

- Add "Airplane mode is on" to sub-title
  - Set the header layout to CENTER_HORIZONTAL if it's no icon

- Hide "Settings" button

- Screenshot
  https://screenshot.googleplex.com/6m5dFVZu7ar4nKW

Bug: 178717651
Test: manual test
atest InternetConnectivityPanelTest \
      PanelFragmentTest \
      ProviderModelSliceTest

Change-Id: I899a817fd99415e9cad608aa4deac1e45365696a