Cosign support

[pvizeli]

Breaking change

The internal images are not pushed to docker.io anymore, as we now do with all other internal images.
If someone did not follow our docs and did something's own on his end, it could be that he use an internal image and not the official one. So it's only a breaking change if he does not use the official images according to our docs over docker.io

Proposed change

Use now cosign to sign the images

Type of change

• Dependency upgrade
• Bugfix (non-breaking change which fixes an issue)
• New integration (thank you!)
• New feature (which adds functionality to an existing integration)
• Deprecation (breaking change to happen in the future)
• Breaking change (fix/feature causing existing functionality to break)
• Code quality improvements to existing code or addition of tests

Additional information

• This PR fixes or closes issue: fixes #
• This PR is related to issue:
• Link to documentation pull request:

Checklist

• The code change is tested and works locally.
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• Tests have been added to verify that the new code works.

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