Breaks out the `network_carrier_aware_avoid_bad_wifi` setting from a single
string key into individual `Global.Settings` entries per subscription ID.
Flag: EXEMPT mainline
Bug: 424330991
Test: atest ConnectivityCoverageTests:android.net.connectivity.android.net.ConnectivitySettingsManagerTest
Change-Id: Ida673c1b8b915719b8e64ea85a66c2b98862e5f5