tests: Bluetooth: CAP and GMAP: Add TX/RX for AC tests

Add TX and RX verification for the audio configuration tests.
This requires modifying some of the underlying structures
used in those tests, as well as initializating and triggering
TX, and with verification of RX as well.

These tests were implemented to ensure that the streams are not
just established, but can send ISO data without issues.

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