Bluetooth: Audio: Shell: Remove csip_set_coordinator init command

Remove the init command for teh CSIP Set Coordinator.
The main reason for this is that we want to ensure that we
register the conn callbacks early so that `conns` array is
properly filled.

The other callbacks registered in the init function
can easily be moved to where they are needed, and even
unregistered to avoid parsing more data than we need.

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