Merge bitcoin/bitcoin#31910: qa: fix an off-by-one in utxo snapshot fuzz target and sanity check its snapshot data

63b534f97e fuzz: sanity check hardcoded snapshot in utxo_snapshot target (Antoine Poinsot)
3b85eba83a test util: split up ConnectBlock from MineBlock (Antoine Poinsot)
d1527f6b88 qa: correct off-by-one in utxo snapshot fuzz target (Antoine Poinsot)

Pull request description:

  The assumeutxo data for the fuzz target could change and invalidate the hash silently, preventing the fuzz target from reaching some code paths. Fix this by introducing a unit test which would break if the snapshot data the fuzz target relies on were to change.

  In implementing this i noticed the height used for coins in the fuzz target is actually off-by-one (as if the first block in the created chain was the genesis but it's block `1`), so fix that too.

ACKs for top commit:
  mzumsande:
    Code Review ACK 63b534f97e
  fjahr:
    tACK 63b534f97e

Tree-SHA512: 2399b6e74db9b78aab8efba67c57a405d2d7d880ae3b7d8518a1c96cc6266f61f5e77722cd999adeac5d3e03e73d84cf9ae7bdbcc0afae198cc87049dde4012f

src/kernel/chainparams.cpp

@@ -589,7 +589,7 @@ public:
             {
                 // For use by fuzz target src/test/fuzz/utxo_snapshot.cpp
                 .height = 200,
-                .hash_serialized = AssumeutxoHash{uint256{"4f34d431c3e482f6b0d67b64609ece3964dc8d7976d02ac68dd7c9c1421738f2"}},
+                .hash_serialized = AssumeutxoHash{uint256{"7e3b7780fbd2fa479a01f66950dc8f728dc1b11f03d06d5bf223168520df3a48"}},
                 .m_chain_tx_count = 201,
                 .blockhash = consteval_ctor(uint256{"5e93653318f294fb5aa339d00bbf8cf1c3515488ad99412c37608b139ea63b27"}),
             },