9408a04e42 tests, fuzz: use new NUMS_H const (josibake)
b946f8a4c5 crypto: add NUMS_H const (josibake)
Pull request description:
Broken out from #28122
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[BIP341](https://github.com/bitcoin/bips/blob/master/bip-0341.mediawiki#constructing-and-spending-taproot-outputs) defines a NUMS point `H` as *H = lift_x(0x50929b74c1a04954b78b4b6035e97a5e078a5a0f28ec96d547bfee9ace803ac0)* which is [constructed](11af7015de/src/modules/rangeproof/main_impl.h (L16)) by taking the hash of the standard uncompressed encoding of the [secp256k1](https://www.secg.org/sec2-v2.pdf) base point G as X coordinate."
Add this as a constant so it can be used in our codebase. My primary motivation is BIP352 specifies a special case for when taproot spends use `H` as the internal key, but outside of BIP352 it seems generally useful to have `H` in the codebase, for testing or other use cases.
ACKs for top commit:
paplorinc:
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theStack:
Code-review ACK 9408a04e42
Tree-SHA512: ad84492f5d635c0cb05bd82546079ded7e5138e95361f20d8285a9ad6e69c10ee2cc3fe46e16b46ef03c4253c8bee1051911c6b91264c90c3b1ad33a824bff4b
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