Bluetooth: Audio: Expand CAP tests for CAP broadcast

Expand the CAP tests to also have a test case for CAP
acceptor and CAP initiator broadcast, which is heavily
inspired from the BAP broadcast tests.

The tests only tests that a broadcast source can be created
with the CAP API and that the metadata is correct.

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