samples: Bluetooth: BAP: BA: Reset states and modify error checking

Modify the reset function to also reset the connection and
PA sync states.

Modify and add missing checks for mutex locks to use ASSERT
when using K_FOREVER, as they should never fail/timeout.

Cleanup some text and error checks.

Ensure that the add_src_param is reset for each loop
iteration as well.

Modify so that we use K_FOREVER fewer places.

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