Ensure proto deduplication does not extend indefinitely

[adriansmares]

Summary

This PR ensures that our uplink deduplication script does not extend the metadata list indefinitely. This would happen because the TTL of the list accumulating the metadata is refreshed every time metadata is pushed, instead of being refreshed only on the first push.

Changes

• Update the metadata list TTL only on the first push.
• Remove some technical debt related to how we mock proto messages in Redis testing. We need to remove this for Migrate away from gogo/protobuf #2798 .

Testing

Unit tests and local testing.

Regressions

N/A.

Checklist

• Scope: The referenced issue is addressed, there are no unrelated changes.
• Compatibility: The changes are backwards compatible with existing API, storage, configuration and CLI, according to the compatibility commitments in README.md for the chosen target branch.
• Documentation: Relevant documentation is added or updated.
• Changelog: Significant features, behavior changes, deprecations and fixes are added to CHANGELOG.md.
• Commits: Commit messages follow guidelines in CONTRIBUTING.md, there are no fixup commits left.