Distributed bus should emit events for monitoring/observation

[autodidaddict]

There are a number of events that might be of interest to observers in lattice and each wascc host should emit those when appropriate:

• Host Up
• Host Down
• Actor Starting
• Actor Started
• Actor Stopped
• Actor Updating (live update/swap)
• Actor Updated (live update/swap)
• Provider Loaded (includes both portable and native)
• Provider Removed
• Dispatch Failed
• Actor Call Failed
• Actor Binding Created
• Actor Binding Removed
• Actor Became Unhealthy
• Actor Became Healthy

These events should probably go on a subject like wasmbus.events, with obvious restrictions in deployed scenarios as to which user credentials are allowed to subscribe to this. For production security purposes, I would recommend that the leaf node credentials used by the leaf node to which wascc hosts connect have publish only rights to the wasmbus.events, which would prevent someone who compromises a leaf node from being able to subscribe to this subject.

It might also make sense to publish these as JSON on the subject in a CloudEvents envelope.