Fix: Correct test workflow and ensure ssh dir exists on service container

- Reverted .github/workflows/test.yml to the correct version which uses GITHUB_OUTPUT for keys, netcat for port checking, and has better service readiness logic.
- Modified the test workflow to explicitly create /root/.ssh directory on the SSH service container before attempting to copy the public key. This resolves potential errors if the directory doesn't exist by default in some edge cases of the service image or its startup.

This addresses the previously reported test failures.

Author: google-labs-jules[bot]