Add `v0` suffix to event types to indicate unstable API

[embano1]

vSphere events are currently not versioned (by the source/emitter) and the API schema might break. Indicate this with a trailing v0 in the event type and add additional context (attribute) to all events reflecting the vSphere API version that generated an event. See vmware-samples/vcenter-event-broker-appliance#439 for details.