Draft: Improve CI

This MR does several things:

1. removes redundant build jobs
2. gives each arch its own job
3. splits docker job into one job per image
4. adds a "push" step to the docker jobs
5. significantly improves the size and build time of the docker images
6. limits docker jobs to only trigger on specific branches
7. extends hidden jobs rather than inheriting default values
8. builds and pushes docker images for multiple architectures, not just amd64

I've also added CI/CD variables to the settings on this repo so the docker jobs can push images to docker hub automatically.

TODO: fix arm architectures