Upload container images to Github Container Registry

[tenzen-y]

As @juliusvonkohout mentioned in kubeflow/manifests#3010, DockerHub will introduce more restricted container image limitations for anonymous users.

So, it would also be better to push all container images to GHCR for bertter UX.

Note: This does not indicate removing images from DockerHub and stopping the push to DockerHub. Both should be maintained.

[tenzen-y]

/kind feature

[thesuperzapper]

@tenzen-y we really need to do this due to the new rate limits on DockerHub (and also because the other Kubeflow projects have already migrated).

For example, here is the trainer PR (kubeflow/trainer#2455) and Issue (kubeflow/trainer#2446)

cc @mahdikhashan @andreyvelich @Electronic-Waste

[mahdikhashan]

I'll fix it @thesuperzapper , thanks for mentioning me here.

[mahdikhashan]

/assign