chore: replace local development broker with redis

[miketheman]

As a means to test and demonstrate that using Redis as a broker is an easy replacement for SQS.

Add flower at http://localhost:5555 to play around with and observe behaviors.

Doesn't touch main runtime dependencies until we decide to retire SQS behaviors, and even then, not much changes other than minor tweaks to the depgraph - we still need all the packages we install anyhow.

Drops the largeish ~2GB localstack docker image

Relates to #13702