Update CircleCI configuration for pushing to container registries

[marians]

Towards giantswarm/roadmap#2979

Context: announcement in #news-dev on Slack

This PR was created through automation by Team Honeybadger, to make sure that the container images built for this repository are available in the right registries.

For that, the CircleCI configuration is modified to use the new push-to-registries job instead of the old push-to-docker. This means that there is only one job for all registry pushes, and it simplifies the configuration by removing many parameters that are now set automatically or as defaults.

Notes

• Since the PR is also changing the CircleCI job name to push-to-registries, the branch protection rules in this repository will likely require updating before the required checks can be green.
• Dev images are sent to ACR (gsoci.azurecr.io) and Quay currently. If you need dev images elsewhere, you can add the according configuration as described in the documentation to the step configuration.

To the responsible team

Please,

• Assign this PR to yourself
• Verify that the check ci/circleci: push-to-registries has been executed successfully.
• Double-check the job dependecies (requires)
• Double-check the job filters. Especially if this PR replaces several jobs with one, and the previous jobs had different filters, make sure that the filter includes all cases.
• Update the changelog if you think this deserves a mention
• Approve and merge this PR once it's ready. No need to wait for the author in this case.

Please get this done until December 5, so that we can move on with the next migration steps. Thank you!

[fiunchinho]

@marians I think this line is not necessary. Can you confirm?

[marians]

Without this line, the image would get pushed with the name giantswarm/aws-pod-identity-webhook after the GitHub repository. So I think it's vital.