Add post-kcp-publish-image job

[xrstf]

This is the sister PR to kcp-dev/kcp#2976, adding the necessary postsubmit.

Images were previously built for main/release branches and for tags ( https://github.com/kcp-dev/kcp/blob/main/.github/workflows/kcp-image.yaml#L8-L12 ), so I kept this behaviour.

[sttts]

/lgtm
/approve

[kcp-ci-bot]

LGTM label has been added.

Git tree hash: 94ca0f8233b1bbc4191d0eb69be5f58b2729bed4

[kcp-ci-bot]

[APPROVALNOTIFIER] This PR is APPROVED

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[kcp-ci-bot]

@xrstf: Updated the job-config configmap in namespace prow at cluster default using the following files:

• key prow-jobs-kcp-kcp-postsubmits.yaml using file prow/jobs/kcp/kcp-postsubmits.yaml

In response to this:

This is the sister PR to kcp-dev/kcp#2976, adding the necessary postsubmit.

Images were previously built for main/release branches and for tags ( https://github.com/kcp-dev/kcp/blob/main/.github/workflows/kcp-image.yaml#L8-L12 ), so I kept this behaviour.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.