fix(rstest): should stringify resource path

[fi3ework]

Summary

Should use stringify to get correct path on win32.

Checklist

• Tests updated (or not required).
• Documentation updated (or not required).

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[codspeed-hq]

CodSpeed Performance Report

Merging #10619 will not alter performance

_{Comparing rstest-1 (5f43d63) with main (a6cb5d0)}

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Summary

✅ 12 untouched benchmarks