requirement: add dynamic-sidecar client using RabbitMQ (enables easier k8s migration)

[GitHK]

Why do this and not reuse the current HTTP interface?

There are currently 2 strong incentives to use RabbitMQ, regardless of any other benefits:

• I don't have to deal with the issue of reusing the same httpx client in the dynamic-scheduler (pools accumulate connections and they have to be terminated after an amount of time, otherwise connections will no longer work)
• Primarily: allowing all the simcore services to run in k8s. Exposing the http interface via RabbitMQ is the way to go to enable this feature, since currently the only way for the dynamic-scheduler to access a dynamic-sidecar is via it's http interface

Since we are moving away all piecev