bluez5: aac: set reasonable default bitrate
Set default bitrate to a reasonable value in caps, and handle the unknown bitrate case configuration selection.
Handling of the bitrate was the other difference in the AAC caps compared to bluez-alsa and @eh5's pulseaudio-modules-bt. From some of the issues it appears there are some devices that have problems with pipewire's aac caps, so it might be possible this is related.