tests: Bluetooth: Audio: Remove netcore logs from nrf53 BSIM

Removes the use of the debug.conf file when building the
tests for the nRF5340, as that will also enable logs and will
log every message between the two cores, making the logs very
verbose.

Copy the lines from debug.conf that we do want to keep
into the bsim specific conf file, and stop using the debug.conf
file.

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