🧪 Add test coverage for jq fallback installation in renv-cache

[MiguelRodo]

🎯 What: Adds test coverage for the ensure_jq fallback logic inside renv-cache's renv-restore-build script, validating the handling of different package managers when jq is missing.
📊 Coverage: Verifies successful code execution paths for apt-get, apk, dnf, and yum.
✨ Result: Enhanced test reliability by utilizing function extraction and subshells to sidestep Docker-in-Docker caching limits imposed on standard integration tests.

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PR created automatically by Jules for task 10400698089474660978 started by @MiguelRodo

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