feat: Use valkey-bundle docker images for modules related test (9.0+)

[edlng]

Summary

Add Docker-based valkey-bundle servers on dedicated ports for module tests (Search, JSON, Bloom, LDAP). Regular tests still run against the source-built server.

On the 9.0 / ubuntu matrix, CI now builds from source (like every other combo) AND pulls the valkey/valkey-bundle Docker image. The source-built server handles all existing tests. The Docker containers run on separate ports (standalone: 6389, cluster: 8001-8006) with modules loaded, and export modules-standalone-endpoint / modules-cluster-endpoints env vars for module-specific tests to pick up.

We tried routing everything through Docker first, but the bundle image is pinned to 9.1-rc1 (no stable 9.0 tag yet) and that caused consistent standalone timeouts. Separate ports and separate servers to handle module-related tests should be sufficient and better.

Issue link

Closes #245

What changed

• New composite action .github/workflows/start-valkey-docker/action.yml. Pulls valkey/valkey-bundle:9.1-rc1, starts standalone (port 6389) and cluster (ports 8001-8006) containers with --network host, forms the cluster, writes endpoint env vars. Uses the source-built valkey-cli already on the host, so no binary extraction needed.
• install-shared-dependencies now always builds from source first. For 9.0 on ubuntu it also runs the Docker action afterward.

Limitations

• 9.1-rc1 pin means module tests hit a pre-release server . TODO in the action to swap once stable tags exist.
• Only 9.0 on ubuntu gets module servers, other combos skip module tests due to limitations with Docker.
• Nothing reads the modules-* env vars yet. feat: Add Valkey Search Support #225.

Testing

Ran the 9.0 / ubuntu matrix three times. Regular tests pass on the source-built server. Docker containers start and respond to PING. TLS tests work via cluster_manager.py + source-built valkey-server. Confirmed ports 6389 and 8001-8006 don't collide with anything in the test suite or cluster_manager.py's random port range.

Checklist

• This Pull Request is related to one issue.
• Commit message has a detailed description of what changed and why.
• Tests are added or updated and all checks pass.
• CHANGELOG.md, README.md, DEVELOPER.md, and other documentation files are updated.
• Destination branch is correct - main or release
• Create merge commit if merging release branch into main, squash otherwise.