Automatically fix scorecard image digests

[nunnatsa]

fix #6428

Description of the change:

• Add a new tool - the "digester", to retrieve the image digest from the registry.
• Add a new Makefile target make build-digester to build the new tool
• Add a new Makefile target make update-scorecard-images to update the hard-coded digests in internal/cmd/operator-sdk/scorecard/cmd.go
• Add a new github action to periodically check for digests changes and open a PR with an update, if needed. This action can also been run manually from github.

Motivation for the change:
The digests in internal/cmd/operator-sdk/scorecard/cmd.go are hard-coded. Since latest is a floating image tag, then each time a new image is pushed, the digest is changed, and then the scorecard stop working.

This PR is trying to mitigate this, by automatically open a PR to update the digests, each time a new image is pushed.

Checklist

If the pull request includes user-facing changes, extra documentation is required:

• Add a new changelog fragment in changelog/fragments (see changelog/fragments/00-template.yaml)
• Add or update relevant sections of the docs website in website/content/en/docs

[nunnatsa]

/hold

[nunnatsa]

not needed. different solution implemented at #6422 and #6425

[nunnatsa]

/close

[openshift-ci]

@nunnatsa: Closed this PR.

In response to this:

/close

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