SettingsBackupAgent: notify of apBand conversion

Added support to notify user of a change to their softap configuration
preferences after being restored via SettingsBackupAgent.

Bug: 80251951
Test: frameworks/opt/net/wifi/tests/wifitests/runtests.sh
Test: manually confirmed configs are converted for different device
Change-Id: I4cec15549d694cdb1a7b09f1426d027eec021122