Investigate feasibility of PTP timing support

[bradkeifer]

Shairport-sync and Juke amplifiers only support PTP timing for their AirPlay2 implementation. The OwnTone implementation of AirPlay2 only supports NTP timing for its AirPlay2 implementation and hence we cannot stream to shairport-sync devices using AirPlay2.
It might be possible to implement a client-side PTP timing capability into OwnTone by reviewing and copying from the PTP implementation from Mike Brady.

See MA issue 4656 for more info.

[bradkeifer]

This is currently on hold whilst @ejurgensen reviews and modifies the approach to supporting a PTP Timing server service. From a Music Assistant perspective, it is necessary to have a PTP Timing server service running on the Music Assistant host that can simultaneously service multiple Airplay 2 devices.

The initial implementation of PTP Timing support for AirPlay 2 devices in OwnTone supports the service running in a single instance of OwnTone only. Subsequently, this is not appropriate for Music Assistant given the 1:1 alignment between an AirPlay 2 device and the cliap2 instance.