Add a docker compose runner for hydrapool's stack

[pool2win]

• Build hydrapool optimised docker image
• Build prom and grafana images for moving configs in there
• Hydrapool config.toml is mounted, so user can provide a new config. Otherwise the defaults from the hydrapool image are used.
• Add github workflow to build images for docker. Once this is done, I'll edit compose file to not build the image, but use the latest or corresponding version one.
• Since this PR is a giant blob, also adding changelog in this PR :)