Worker does not template ECSTask family

[EmilRex]

PR #152 changed the behavior of the family top-level settings on the ECSTask infrastructure block. Rather than just being set to prefect, it instead templates using the flow and deployment names: prefect__{flow-name}__{deployment-name}. This change does not seem to have made it into the worker. When users have multiple heterogeneous deployments, using a single family (prefect) can lead to excessive task definition revisions and may trigger service rate limits.

[bennnym]

any progress on this @EmilRex - feels quite silly having to input a family override for each deployment as a hot fix...