[CHORE] Switch to setup-docker-builder action

[rescrv]

Description of changes

Blacksmith pointed out we're not using caching to our advantage.

Test plan

CI + Review

Migration plan

N/A

Observability plan

N/A

Documentation Changes

N/A

[github-actions]

Reviewer Checklist

Please leverage this checklist to ensure your code review is thorough before approving

Testing, Bugs, Errors, Logs, Documentation

• Can you think of any use case in which the code does not behave as intended? Have they been tested?
• Can you think of any inputs or external events that could break the code? Is user input validated and safe? Have they been tested?
• If appropriate, are there adequate property based tests?
• If appropriate, are there adequate unit tests?
• Should any logging, debugging, tracing information be added or removed?
• Are error messages user-friendly?
• Have all documentation changes needed been made?
• Have all non-obvious changes been commented?

System Compatibility

• Are there any potential impacts on other parts of the system or backward compatibility?
• Does this change intersect with any items on our roadmap, and if so, is there a plan for fitting them together?

Quality

• Is this code of a unexpectedly high quality (Readability, Modularity, Intuitiveness)

[propel-code-bot]

Switch from build-push-action to setup-docker-builder for Blacksmith

This pull request updates the project's GitHub Actions workflows and composite actions to replace the use of useblacksmith/build-push-action@v2 (with setup-only: true) with the dedicated useblacksmith/setup-docker-builder@v1 action. The refactoring primarily affects the Docker setup step in CI and release build workflows, intending to make use of improved Docker builder caching as suggested by Blacksmith. No logic changes are introduced outside build pipeline configuration, and there are no application/runtime code modifications.

Key Changes

• Removed setup-blacksmith input from .github/actions/docker/action.yaml and its support code.
• Replaced direct uses of useblacksmith/build-push-action@v2 (with setup-only) with useblacksmith/setup-docker-builder@v1 in .github/actions/docker/action.yaml, .github/workflows/nightly-tests.yml, and .github/workflows/_build_release_container.yml.
• Updated all affected workflows to remove unused or redundant variables pertaining to Blacksmith setup.

Affected Areas

• .github/actions/docker/action.yaml
• .github/workflows/nightly-tests.yml
• .github/workflows/_build_release_container.yml

This summary was automatically generated by @propel-code-bot