Deprecate DockerHub and Anaconda.org use

[j-wags]

• Fixes Switch Docker image push to use GHCR, deprecate DockerHub #328
• Removes use of anaconda.org
• Updates docs

[j-wags]

I was able to successfully deploy ddx-containing workers for the MLPepper dataset using the stuff from this PR, so I think this is basically done modulo docs updates. But I'm going to focus on fixing #370 first since the reporting in that will give us some insight into whether the newly deployed workers are successful at scale.