~~It's only needed for a hardcoded int, which we can define locally.~~
Note from Backporter: Core's description of this is indeed somewhat confusing. nScriptCheckThreads is removed in the next commit.
https://github.com/bitcoin/bitcoin/pull/17342/commits/d9957623b48a7c3eff0ac750d1245fabfb1843a2
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Partial backport of Core [[https://github.com/bitcoin/bitcoin/pull/17342 | PR17342]]