Add Chronyd Sync Module - UG1602

Support for operating alongside the chronyd service is now provided in a separate crny sync module. For example:

[general]
sync_module crny crny1

To aid the transition from existing behavior under the NTP sync module, sfptpd implicitly creates a suitable instance of the crny sync module. If this instance is not required you should disable it by specifying a crny sync module with no instances:

[general]
sync_module crny

This gives better performance, and simplified logging and diagnostics.

See the sync_module option in Configuration Options, Chronyd Sync Module, and Chronyd.