Do not skip parent display-based style fixups for NAC that is not a NAC root
Stylo is currently skipping parent display-based style fixups for all NAC,
whereas we probably only want to do this for NAC roots.
In this patch, we ensure that we skip it for NAC roots, and pseudo-elements,
but not other NAC.
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- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] These changes fix [Bug 1359303](https://bugzilla.mozilla.org/show_bug.cgi?id=1359303)
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cb4ce93429
