Add new pipeline to test elastic-package with integrations repository

[mrodm]

This PR adds a new pipeline elastic-package-test-with-integrations for Buildkite. This pipeline is intended to check a specific version of elastic-package with all the defined packages in the integrations repository

This PR includes:

• Add the new pipeline and its settings into catalog-info.yaml
• Add a new configuration entry for the bot: just allowing running on comments
  • Examples of valid comments:
    • buildkite test integrations
    • test integrations
• Add a minimal pipeline with just one step as a placeholder (.buildkite/test-with-integrations-repo.yml)

[elasticmachine]

💚 Build Succeeded

• Buildkite Build
• Commit: 210f3b3

cc @mrodm