WIP: GHA: Docker workflow refactor

[danielhollas]

This is an analogous refactor that I did over at aiidalab-docker-stack, please see that PR for details. aiidalab/aiidalab-docker-stack#439

tl;dr This should both increase speed and robustness of the build, main due to:

1. Not uploading image as artifacts. (this does have a side-effect that the build can't happen from forks, maybe we can workaround that)
2. Build multiplatform images together

[sphuber]

@unkcpz since you wrote these workflows, maybe it makes most sense if you review this? Happy to do it if you don't have the time

[unkcpz]

Sure, I'll do the review when it is ready.

[danielhollas]

@unkcpz I just realized, we're probably going to need an extra buildjet account for aiidateam org, right?

[unkcpz]

Yes, it is run using a separated account. But I guess you don't access to the dashboard to set it?

[danielhollas]

I don't think so, since I am not a member of aiidateam I don't think. But if it is already setup that's great.

[danielhollas]

@sphuber do you think you could (temporarily) give me a push access to this repo? Otherwise this PR is hard to test.

[sphuber]

@sphuber do you think you could (temporarily) give me a push access to this repo? Otherwise this PR is hard to test.

Done

[danielhollas]

Thanks @sphuber. Opened #6396, closing this one.

[unkcpz]

(this does have a side-effect that the build can't happen from forks, maybe we can workaround that)

As mentioned in another thread (aiidalab/aiidalab-qe#730), since the test was run before by PR from forked repo, then I'd be a bit disappointed this functionality disappeared.

There is an solution that we can use to allow to use the GITHUB_TOKEN by PR from the forked repo. It is called pull_request_target. It confines the PR from forked repo to run actions only when the specified files are modified.
I tested it in https://github.com/aiidateam/aiida-registry/blob/master/.github/workflows/plugin-ci.yml to allow plugin developers to trigger the PR preview when adding plugin to registry, only changes of plugins.yaml will trigger the CI (Note: this is not the same as when using pull_request with path.) In this way, the GITHUB_TOKEN can be used to push things to registry.