Event stream backed query handlers

[MerrionComputing]

Allow for a query handler to have an event stream backing it with the steps of handling the query appended onto that event stream.

Domain: Query Entity Type: Query Name Instance Identifier: {GUID}

[MerrionComputing]

Each query will need a Query Processing Requested event to trigger any downstream processing - for example you might have a "cache watcher" that just responds with a cached value if the precise same question has already been asked.