maint: add a docker'd Redis TLS local setup

[robbkidd]

Which problem is this PR solving?

• make it easy to run a TLS'd Redis locally in development
• maybe a foundation for smoke-tests later

Short description of the changes

• add a make target for building the Docker image locally like CI does for releases
• add a docker-compose config in a new smoke-tests/ directory
  • redis is run with TLS enabled using self-signed certs generated as needed by the gen-certs service container

[kentquirk]

I know this is still in draft, but please add a README to the folder explaining how to use it?

[VinozzZ]

I tested this on my machine and it works great