Configurable syslog targets

[stgraber]

Not everyone likes using Grafana Loki for logging. A common alternative which works as a protocol with most log management systems is good old syslog.

It would be good to extend our internal logging/event forwarding mechanism to also work over syslog.

I suspect we may want something like this:

• logging.syslog.NAME.target (address of the remote syslog server)
• logging.syslog.NAME.facility (syslog facility to use for the forwarded events)
• logging.syslog.NAME.severity (syslog severity to use for the forwarded events, if not specified, info is used unless we have an internal severity already)
• logging.syslog.NAME.type (logging, lifecycle or network-acl)
• logging.syslog.NAME.loglevel (minimum log level when forwarding logging events)

(Once this lands, we'll want to standardize LOKI and move it to logging.loki.NAME.XYZ instead of its current single-server top-level at loki.*)