Add Builder v4 Parity Docs for Test Runner

[AndrewKahr]

Changes

• Add containerRegistryRepository, containerRegistryImageVersion, chownFilesTo, and runAsHostUser

Checklist

• [x] Read the contribution guide and accept the code of conduct
• [x] Readme (updated or not needed)
• [x] Tests (added, updated or not needed)

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Visit the preview URL for this PR (updated for commit 569ae95):

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