test: add tests for monorepo base path

[lukasholzer]

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Summary

Add tests for setting the package_path on monorepos

Follow up for #6404

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[github-actions]

📊 Benchmark results

Comparing with fd70ac4

• Dependency count: 1,345 (no change)
• Package size: 313 MB ⬆️ 0.00% increase vs. fd70ac4
• Number of ts-expect-error directives: 1,001 (no change)