Merge bitcoin/bitcoin#23997: wallet: avoid rescans under assumed-valid blocks

817326a828 wallet: avoid rescans if under the snapshot (James O'Beirne)

Pull request description:

  This is part of the [assumeutxo project](https://github.com/bitcoin/bitcoin/projects/11) (parent PR: #15606)

  ---

  Refuse to load a wallet if it requires a rescan lower than the height of assumed-valid blocks.

  Of course in live code right now, `BLOCK_ASSUMED_VALID` block index entries don't exist since they're a unique flag introduced by the use of UTXO snapshots, so this is prophylactic code exercised only by unittests.

ACKs for top commit:
  achow101:
    ACK 817326a828
  ryanofsky:
    Code review ACK 817326a828. This seems like the simplest change we can make to avoid wallet problems when an assumeutxo snapshot is loaded.

Tree-SHA512: cfa44b2eb33d1818d30df45210d0dde1e9b78cc9b7c88cb985054dc28427bba9e0905debe4196065d1d3a5ce7bca7e605e629d5ce5f0225b25395746e6d3d596

src/node/interfaces.cpp

@@ -775,6 +775,11 @@ public:
             notifications.transactionAddedToMempool(entry.GetSharedTx(), 0 /* mempool_sequence */);
         }
     }
+    bool hasAssumedValidChain() override
+    {
+        return Assert(m_node.chainman)->IsSnapshotActive();
+    }
+
     NodeContext& m_node;
 };
 } // namespace