Merge bitcoin/bitcoin#30329: fuzz: improve utxo_snapshot target

de71d4dece fuzz: improve utxo_snapshot target (Martin Zumsande)

Pull request description:

  Add the possibility of giving more guidance to the creation of the metadata and/or coins, so that the fuzzer gets the chance
  to reach more error conditions in ActivateSnapshot and sometimes successfully creates a valid snapshot.

  This also changes the asserts for the success case that were outdated (after #29370) and only didn't result in a crash because the fuzzer wasn't able to reach this code before.

ACKs for top commit:
  maflcko:
    re-ACK de71d4dece 🎆
  fjahr:
    utACK de71d4dece
  TheCharlatan:
    ACK de71d4dece

Tree-SHA512: 346974d594164544d8cd3df7d8362c905fd93116215e9f5df308dfdac55bab04d727bfd7fd001cf11318682d11ee329b4b4a43308124c04d64b67840ab8a58a0

src/kernel/chainparams.cpp

@@ -495,12 +495,19 @@ public:
         };
 
         m_assumeutxo_data = {
-            {
+            {   // For use by unit tests
                 .height = 110,
                 .hash_serialized = AssumeutxoHash{uint256S("0x6657b736d4fe4db0cbc796789e812d5dba7f5c143764b1b6905612f1830609d1")},
                 .nChainTx = 111,
                 .blockhash = uint256S("0x696e92821f65549c7ee134edceeeeaaa4105647a3c4fd9f298c0aec0ab50425c")
             },
+            {
+                // For use by fuzz target src/test/fuzz/utxo_snapshot.cpp
+                .height = 200,
+                .hash_serialized = AssumeutxoHash{uint256S("0x4f34d431c3e482f6b0d67b64609ece3964dc8d7976d02ac68dd7c9c1421738f2")},
+                .nChainTx = 201,
+                .blockhash = uint256S("0x5e93653318f294fb5aa339d00bbf8cf1c3515488ad99412c37608b139ea63b27"),
+            },
             {
                 // For use by test/functional/feature_assumeutxo.py
                 .height = 299,