Can not reset subscription if there are multiple runners for a deployment

[matt2e]

When resetting a subscription we must do this via the runners which have a claim on each partition for the consumer group. We do not have a way currently for calling each runner within a deployment. Instead it currently calls the endpoint for the deployment which will reach only one runner.

[alecthomas]

Should this be passed through the DeploymentContext? That seems like a bad idea. Think about it.

[alecthomas]

Another use case is eg. ensuring all runners have a consistent view of secrets/configs, which has been a problem in the past. Is this the same problem/use case? Figure it out.