Add --image-name-tag-with-digest flag

[Or-Geva]

Description
Added --image-name-tag-with-digest-file to write image:tag@sha256:... names based on destinations specified.

New flag will write a line for each destination specified. This is the full image path (ie, a docker registry will start with index.docker.io/{USER}/{IMAGE}:{TAG}@sha256:__)

Submitter Checklist

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• Includes unit tests
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Reviewer Notes

• The code flow looks good.
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Release Notes

Describe any changes here so maintainer can include it in the release notes, or delete this block.

Examples of user facing changes:
- kaniko adds a new flag `--image-name-tag-with-digest-file` to specify a file to save the image name w/ image tag and digest of the built image to.

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[Or-Geva]

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