CI: Add Modules Testing

[edlng]

ci(php): add Docker-based CI for Valkey Search module testing

Summary

Adds a reusable GitHub Actions composite action (start-valkey-docker) that spins up standalone, cluster, and auth-protected Valkey servers using Docker with the valkey-bundle image (which includes the Search module). Updates the CI workflows to use Docker containers for Valkey 9.0 on Ubuntu, falling back to native server startup for other versions/platforms.

This is independent of the search command PRs and can be merged separately.

Issue link

Closes #165

Features / Behaviour Changes

• New .github/workflows/start-valkey-docker/action.yml composite action
  • Pulls valkey/valkey-bundle:9.1-rc1 (pinned until stable 9.x images ship)
  • Starts standalone (6379-6381 with replication), cluster (7001-7006), and auth cluster (5001-5006)
  • Sets up TLS servers when valkey-server is available on the host
  • Falls back to native startup when Docker isn't available (macOS)
  • Extracts valkey-cli from the image for cluster creation and health checks
• Updated php.yml to use Docker for 9.0+ubuntu, native for everything else
• Updated test-pecl-package and test-pie.yml to use the new action
• Cleaned up server stop steps to handle both Docker containers and native processes
• Removed stale debug logging from run-php-tests

Implementation

The action checks Docker availability first, then either pulls the bundle image and starts containers with --network host, or falls back to the existing shell scripts. TLS setup always uses the host valkey-server binary (built from source by install-engine) since the Alpine binary from the Docker image may not work on Ubuntu.

Limitations

• Image is pinned to valkey-bundle:9.1-rc1. Needs updating when stable 9.x images are published.
• TLS setup depends on valkey-server being available on the host. So, these tests use the built-from-source server.

Testing

Tested in CI across the matrix (Ubuntu + macOS, multiple engine versions, PHP 8.2/8.3). Docker path runs on Ubuntu with 9.0, native path runs everywhere else.

Checklist

Before submitting the PR make sure the following are checked:

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