test: update BIP340 test vectors and implementation (variable-length messages) #32642

1. 
   theStack commented at 0:04 am on May 30, 2025: contributor

   This PR updates the Schnorr signatures implementation in the functional test framework to the latest BIP changes (see https://github.com/bitcoin/bips/pull/1446,commit 200f9b26fe0a2f235a2af8b30c4be9f12f6bc9cb) and syncs the test vectors accordingly. Practically, we probably don’t need non-32-bytes message signing/verifying any time soon, but it seems good practice anyways to update.
2. test: update BIP340 test vectors and implementation (variable-length messages)

   See https://github.com/bitcoin/bips/pull/1446,
   commit 200f9b26fe0a2f235a2af8b30c4be9f12f6bc9cb

   b184f5c87c
3. 
   DrahtBot commented at 0:04 am on May 30, 2025: contributor

   The following sections might be updated with supplementary metadata relevant to reviewers and maintainers.

   Code Coverage & Benchmarks

   For details see: https://corecheck.dev/bitcoin/bitcoin/pulls/32642.

   Reviews

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   ACK	real-or-random, jonasnick

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4. DrahtBot added the label Tests on May 30, 2025
5. 
   fanquake commented at 9:49 am on May 30, 2025: member

   cc @sipa @real-or-random @jonasnick
6. real-or-random approved
7. 
   real-or-random commented at 12:02 pm on May 30, 2025: contributor

   utACK b184f5c87c418ea49429e4ce0520c655d458306b

   In the long run, it may make sense to depend on (and perhaps vendor) https://github.com/secp256k1lab/secp256k1lab for the EC parts of the test framework. It’s essentially an improved version of @sipa’s EC test framework code.

8. 
   jonasnick commented at 3:00 pm on June 9, 2025: contributor

   utACK b184f5c87c418ea49429e4ce0520c655d458306b

Contributors
theStack DrahtBot fanquake real-or-random jonasnick

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