Redfish event support

[AmateurECE]

I've designed a solution for generating events using tokio's tracing crate. The idea here is that services generate Redfish events with the tracing macros, and we can write services that receive that trace data and fulfill the contract of the EventService--sending those events to remote hosts, etc.

This feature is partially implemented on develop at the moment, but some critical components are missing:

• We need a way to "deserialize" a valuable::Value into an object of type RedfishEvent. I've opened Constructing objects from Value tokio-rs/valuable#128 to kick off the conversation about getting support for this upstream, but I may seek to publish my own crate that implements this functionality if necessary.
• Standard services to receive the tracing data. Right now, I have minimal implementations of these in my git stash. Full implementations should be added to seuss.