fix: consider exclueded file in COPY --from cache keys #2615

[massimeddu-sj]

Fixes #2615

Description

This PR consider excluded files when kaniko calculates the cache key for COPY --from command.

Submitter Checklist

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• [ ] Includes unit tests
• [ ] Adds integration tests if needed.

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Reviewer Notes

• [ ] The code flow looks good.
• [ ] Unit tests and or integration tests added.

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 `--registry-repo` to override registry