ref(docker): use cache mounts for build cache

[gustavovalverde]

Motivation

We've been using external tools and custom approaches to improve the caching layers in Rust, and avoid invalidating the caches if no Rust-code is changed.

This update eliminates the need for external tools like cargo-chef to leverage caching layers, resulting in an average build time reduction of 4m30s (~36% improvement).

While this solution doesn't fully resolve the issues mentioned in #6169 (comment), it represents the best possible approach without resorting to custom solutions, which we'd prefer to avoid.

Depends-On: #8817
Closes #6169

Specifications & References

• https://docs.docker.com/language/rust/develop/

Solution

• Use cache mounts instead of cargo-chef
• Remove custom rsync steps

Others

• Add a RUST_VERSION arg so we don't invalidate our cache so frequently with Rust upgrades
• Use --link in our runtime stage, to reduce the resulting artifact
• Remove the installation of Google OS Config agent, as this is no longer required

Tests

• Tests are passing for CI and CD deployments
• Rebuilding is taking less time (~8 minutes instead of ~13 minutes)

Follow-up Work

• Do not run our runtime stage with the root user
• Add SBOM and provenance attestations https://docs.docker.com/build/ci/github-actions/attestations/

PR Author's Checklist

• The PR name will make sense to users.
• The PR provides a CHANGELOG summary.
• The solution is tested.
• The documentation is up to date.
• The PR has a priority label.

PR Reviewer's Checklist

• The PR Author's checklist is complete.
• The PR resolves the issue.

[gustavovalverde]

@arya2 this one is ready now

[mpguerra]

Do we want to close #6169 with this PR or are we planning on making any other improvements in the short term?

[gustavovalverde]

I've just linked #6169, for automatic closure.

This is not solving the underlying issue, but this is as far as we can get right now, until the mtime issue is solved in Rust.

[arya2]

This looks good!