Merge bitcoin#24102: mempool: Run coin.IsSpent only once in a row

fa2bcc4 Run coin.IsSpent only once in a row (MarcoFalke)

Pull request description:

  Follow-up to commit 64e4963 and bitcoin#23976 (comment)

ACKs for top commit:
  glozow:
    utACK fa2bcc4, agree the assertion is sufficient
  theStack:
    Code-review ACK fa2bcc4
  w0xlt:
    crACK bitcoin@fa2bcc4
  shaavan:
    Code Review ACK fa2bcc4
  brunoerg:
    crACK fa2bcc4

Tree-SHA512: 3be9d6b313bf6bb835f031826c81777b4659118d839001d084e72462391cb64ba81d06a5e07fd21fcfb709a71b08892b23212a98604ce8481da489476b72f072

Author: MarcoFalke

src/validation.cpp

@@ -384,10 +384,10 @@ void CChainState::MaybeUpdateMempoolForReorg(
                 auto it2 = m_mempool->mapTx.find(txin.prevout.hash);
                 if (it2 != m_mempool->mapTx.end())
                     continue;
-                const Coin &coin = CoinsTip().AccessCoin(txin.prevout);
+                const Coin& coin{CoinsTip().AccessCoin(txin.prevout)};
                 assert(!coin.IsSpent());
                 const auto mempool_spend_height{m_chain.Tip()->nHeight + 1};
-                if (coin.IsSpent() || (coin.IsCoinBase() && mempool_spend_height - coin.nHeight < COINBASE_MATURITY)) {
+                if (coin.IsCoinBase() && mempool_spend_height - coin.nHeight < COINBASE_MATURITY) {
                     return true;
                 }
             }