test(jest): simplify Jest snapshotPathNormalizer.ts

[slorber]

Motivation

While working on #11042 I noticed Jest snapshot path normalizer is a bit uselessly complex, and has multiple synchronous fs.realpathSync calls for each path to normalize.

It turns out we may not need that "getRealPath" logic

Also, I'm normalizing windows/posix paths as a first-step, because on the linked PR I had snapshot differences like this one on Windows:

Test Plan

CI

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