message: fuzz: Fix tx_pool target to properly fuzz immature outpoints
diff: namespace {
  const TestingSetup* g_setup;
  -std::vector<COutPoint> g_outpoints_coinbase_init;
  +std::vector<COutPoint> g_outpoints_coinbase_init_mature;
  +std::vector<COutPoint> g_outpoints_coinbase_init_immature;
  struct MockedTxPool : public CTxMemPool {
  void RollingFeeUpdate()
  @@ -34,7 +35,10 @@ void initialize_tx_pool()
  for (int i = 0; i < 2 * COINBASE_MATURITY; ++i) {
  CTxIn in = MineBlock(g_setup->m_node, P2WSH_OP_TRUE);
  // Remember the txids to avoid expensive disk acess later on
  - g_outpoints_coinbase_init.push_back(in.prevout);
  + auto& outpoints = i < COINBASE_MATURITY ?
  + g_outpoints_coinbase_init_mature :
  + g_outpoints_coinbase_init_immature;
  + outpoints.push_back(in.prevout);
  }
  SyncWithValidationInterfaceQueue();
  }
  @@ -86,9 +90,8 @@ FUZZ_TARGET_INIT(tx_pool_standard, initialize_tx_pool)
  std::set<COutPoint> outpoints_rbf;
  // All outpoints counting toward the total supply (subset of outpoints_rbf)
  std::set<COutPoint> outpoints_supply;
  - for (const auto& outpoint : g_outpoints_coinbase_init) {
  + for (const auto& outpoint : g_outpoints_coinbase_init_mature) {
  Assert(outpoints_supply.insert(outpoint).second);
  - if (outpoints_supply.size() >= COINBASE_MATURITY) break;
  }
  outpoints_rbf = outpoints_supply;
  @@ -253,13 +256,12 @@ FUZZ_TARGET_INIT(tx_pool, initialize_tx_pool)
  const auto& node = g_setup->m_node;
  std::vector<uint256> txids;
  - for (const auto& outpoint : g_outpoints_coinbase_init) {
  + for (const auto& outpoint : g_outpoints_coinbase_init_mature) {
  txids.push_back(outpoint.hash);
  - if (txids.size() >= COINBASE_MATURITY) break;
  }
  for (int i{0}; i <= 3; ++i) {
  // Add some immature and non-existent outpoints
  - txids.push_back(g_outpoints_coinbase_init.at(i).hash);
  + txids.push_back(g_outpoints_coinbase_init_immature.at(i).hash);
  txids.push_back(ConsumeUInt256(fuzzed_data_provider));
  }
  