[Provider Model] Add WiFi toggle in internet panel

- Move Wi-Fi toggle from menu button to slice row

- Remove Wi-Fi disconnect action

- Show scanning sub-title once only

Bug: 189912933
Test: manual test
atest -c InternetConnectivityPanelTest \
         ProviderModelSliceTest

Change-Id: I2baf05362f5cd0a8ce94c7b3b2b112a7e9fe6894