Bluetooth: Audio: Enable CAP acceptor for shell and bsim

Enable the CAP acceptor for the audio shell configuration
and the babblesim test cases.

Enabling CAP does add some additional requirements, and if
a BAP unicast client attempts to use it without conforming to
those requirement, it won't be able to update the metadata.

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