Fix resolution of implicit relative import when using safe_load_namespace

[desertaxle]

safe_load_namespace had trouble loading implicitly relative import (e.g. from constants import FOO) because the current working directory wasn't included in the sys path when attempting to resolve imports. This PR fixes that.

Closes #15352

Checklist

• This pull request references any related issue by including "closes <link to issue>"
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[cicdw]

makes sense, LGTM

[codspeed-hq]

CodSpeed Performance Report

Merging #15358 will not alter performance

_{Comparing fix-implicit-relative-imports-safe-load (165a8df) with main (ed6d2d7)}

Summary

✅ 3 untouched benchmarks