Convert tests using createNext -> nextTestSetup (#93767)
## What?
Converts existing `createNext()` usage into `nextTestSetup()`.
`createNext()` was the setup step we had before `nextTestSetup()` was
added.
This PR focused on the simple conversion cases. There will be a
follow-up to complete the last few.
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Co-authored-by: Cursor <cursoragent@cursor.com>
