Docker image optimizations

[decimalator]

Descriptive summary

Our Docker images are pretty massive. The Surfliner team has shared some of their optimizations. We should spend some time using the same techniques in our containers.

Smaller images will help improve build and upload times, lower storage use across the cluster and make container boot times much faster.

https://gitlab.com/surfliner/surfliner/-/blob/comet-docker/comet/Dockerfile