Bluetooth: Audio: Integrate scan deletagor and broadcast sink

This integrates the Scan Delegator functionality with the
Broadcast Sink functionality. The Broadcast Sink will
automatically update the receive state for the PA and BIG
sync values, based on state of the Broadcast Sink.

Similarly, a request to terminate the BIG or PA sync from
a Broadcast Assistant will terminate the Broadcast Sinks'
PA or BIG syncs.

Signed-off-by: Emil Gydesen <emil.gydesen@nordicsemi.no>