test: fix single test runner regression

When ESM support was added it created a regression in the test runner
that broke the ability to run individual tests. This commit
re-introduces the use of `NormalizePath` which fixes the regression
in the test runner

Refs: https://github.com/nodejs/node/pull/15300
PR-URL: https://github.com/nodejs/node/pull/15329


Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Gibson Fahnestock <gibfahn@gmail.com>
Reviewed-By: Myles Borins <myles.borins@gmail.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>