Bluetooth: audio: host: call the stream disable callback

Even though the ASCS Sink ASE state machine does not enter the disabling
state according to ASCS spec, it still makes sense to do so.

the state transition unit tests are updated to verify calling or not
calling the disable callback, depending on the transition of the state

fixes #63230

Signed-off-by: Andries Kruithof <andries.kruithof@nordicsemi.no>