Add static assertion that uint32_t is unsigned int or wider
Add static assertion that uint32_t is unsigned int or wider

Summary:
This is a backport of secp256k1 [[https://github.com/bitcoin-core/secp256k1/pull/818 | PR818]]

Depends on D7632

Test Plan:
  ninja check-secp256k1

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D7635

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