Merge bitcoin/bitcoin#33636: wallet: Expand MuSig test coverage and follow-ups

217dbbbb5e test: Add musig failure scenarios (Fabian Jahr)
c9519c260b musig: Check session id reuse (Fabian Jahr)
e755614be5 sign: Remove duplicate sigversion check (Fabian Jahr)
0f7f0692ca musig: Move MUSIG_CHAINCODE to musig.cpp (Fabian Jahr)

Pull request description:

  This is a follow-up to #29675 and primarily adds test coverage for some of the most prominent failure cases in the last commit.

  The following commits address a few left-over nit comments that didn't make it in before merge.

ACKs for top commit:
  achow101:
    ACK 217dbbbb5e
  rkrux:
    lgtm ACK 217dbbb

Tree-SHA512: d73807bc31791ef1825c42f127c7ddfbc70b2b7cf782bc11341666e32e86b787ffc7aed64caea992909cef3a85fc6629282d8209c173aadec77f72fd0da96c45

src/script/sign.cpp

@@ -87,8 +87,6 @@ std::optional<uint256> MutableTransactionSignatureCreator::ComputeSchnorrSignatu
 
 bool MutableTransactionSignatureCreator::CreateSchnorrSig(const SigningProvider& provider, std::vector<unsigned char>& sig, const XOnlyPubKey& pubkey, const uint256* leaf_hash, const uint256* merkle_root, SigVersion sigversion) const
 {
-    assert(sigversion == SigVersion::TAPROOT || sigversion == SigVersion::TAPSCRIPT);
-
     CKey key;
     if (!provider.GetKeyByXOnly(pubkey, key)) return false;
 
@@ -342,7 +340,7 @@ static bool SignMuSig2(const BaseSignatureCreator& creator, SignatureData& sigda
                 sigdata.musig2_partial_sigs[pub_key_leaf_hash].emplace(part_pk, partial_sig);
             }
         }
-        // If there are any partial signatures, exit early
+        // If there are any partial signatures, continue with next aggregate pubkey
         auto partial_sigs_it = sigdata.musig2_partial_sigs.find(pub_key_leaf_hash);
         if (partial_sigs_it != sigdata.musig2_partial_sigs.end() && !partial_sigs_it->second.empty()) {
             continue;