test: Add additional integration tests

[timfish]

• Adds 6 missing integration tests from the old test suite covering edge cases and bundler-specific functionality
• Adds CJS specific tests
• readAllFiles was modified to recursively read from subdirectories

[github-actions]

Semver Impact of This PR

🟢 Patch (bug fixes)

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Internal Changes 🔧

• Add additional integration tests by timfish in #914

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