bluez5: backend-ofono: Add mSBC support

oFono tries to use the best codec when setting up the audio connection, so
the codec to use is known during call to `acquire` function, after the
transport has been created.
To get the codec before creating the transport, an audio connection is
set-up and discarded during `ofono_audio_card_found()`. It should return
the best codec available, which should not change during the time the
remote is connected.

mSBC can be enabled by passing "bluez5.msbc-support=true" parameter to
pipewire-media-session.
mSBC is automatically selected if remote device supports it.