feat(composer): pause/unpause DAGs in one operation

[dkurzaj]

Description

Fixes #10805

When the Airflow instance version is >= 2.9.0 it now uses only one environments.executeAirflowCommand operation (consuming 25 write quota units) for all the DAGs, instead one operation per DAG. It's also way faster (during experimentation, it took 13,54ms per DAG to pause with the new method).

Checklist

• [x] I have followed Sample Guidelines from AUTHORING_GUIDE.MD
• [x] README is updated to include all relevant information
• [ ] Tests pass: nox -s py-3.9 (see Test Environment Setup)
• [ ] Lint pass: nox -s lint (see Test Environment Setup)
• [ ] These samples need a new API enabled in testing projects to pass (let us know which ones)
• [ ] These samples need a new/updated env vars in testing projects set to pass (let us know which ones)
• [ ] This sample adds a new sample directory, and I updated the CODEOWNERS file with the codeowners for this sample
• [ ] This sample adds a new Product API, and I updated the Blunderbuss issue/PR auto-assigner with the codeowners for this sample
• [x] Please merge this PR for me once it is approved

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[gemini-code-assist[bot]]

Summary of Changes

Hello @dkurzaj, I'm Gemini Code Assist[^1]! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request significantly enhances the Cloud Composer DAG management script by enabling the pausing or unpausing of all DAGs in an environment with a single command. The change intelligently detects the Airflow version to apply the most efficient method: new bulk operations for modern Airflow versions (2.9.0+) and the existing iterative approach for older versions. This improvement streamlines DAG management and ensures compatibility across different Composer environments.

Highlights

• Bulk DAG Operations: Introduced new static methods pause_all_dags and unpause_all_dags in composer_dags.py to allow pausing or unpausing all DAGs within a Google Cloud Composer environment in a single operation, leveraging gcloud commands with regex.
• Airflow Version Compatibility: Implemented logic to differentiate between Airflow versions. For Airflow versions 2.9.0 and above, the new bulk operations are used. For older versions, the existing per-DAG iteration logic is maintained to ensure backward compatibility.
• Code Refactoring: The main function in composer_dags.py was refactored to separate the version-specific logic into legacy_operations and modern_operations functions, improving code organization and readability.

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[dkurzaj]

I don't know why all the Kokoro CI checks are pending with: "Expected — Waiting for status to be reported"