Join a READY listener MRP attribute when we recveive the transmit
response.
Also listen for talker attributes.
Remove attribute callbacks, we don't need them because we moved the
packet construction in the MRP users.
Implement notify for listener attributes.
A connect will now make my MOTU send samples to PipeWire.
Remove some of the json parsing for now, work with descriptors.
Remove some parsing code.
Implement GET_AVB_INFO.
Keep descriptors in a list.
Add some utils.
