ci: Publish to quay.io

[Techassi]

Part of stackabletech/issues#716, the repository layout is based on https://github.com/stackabletech/decisions/issues/83.

This PR adds quay.io as a publish target for all product container image builds. With that, we can natively push the images to quay.io instead of mirroring them from our Harbor instance.

Test CI run: https://github.com/stackabletech/docker-images/actions/runs/26161872014

[dervoeti]

Basically LGTM, but:

• Did you take a look at build_spark-connect-client.yaml? It does not get pushed to quay but it's also in the stackable repository (not sdp) so maybe that's on purpose.

• It seems like robot accounts on quay.io need to match a certain regex so the current name would fail? I just tested this with my own account:

[Techassi]

Did you take a look at build_spark-connect-client.yaml? It does not get pushed to quay but it's also in the stackable repository (not sdp) so maybe that's on purpose.

Yeah, I think that is mostly an internal thing. I'm fine not pushing it to quay.io, but I'm also happy to push it - it is basically a decision we have to make.

It seems like robot accounts on quay.io need to match a certain regex so the current name would fail? I just tested this with my own account:

The names should be fine, because I created the robot accounts using these names. Maybe it fails because they already exist?

[dervoeti]

Yeah, I think that is mostly an internal thing. I'm fine not pushing it to quay.io, but I'm also happy to push it - it is basically a decision we have to make.

Okay, we can decide later, won't block this PR for this.

The names should be fine, because I created the robot accounts using these names. Maybe it fails because they already exist?

Ah! They get the stackable+ prefix from quay. Then it works.