message: [refactor] add option to disable RBF
  This is a mere refactor for now. We will use this to disable RBFing in
  package validation.
diff: @@ -459,6 +459,8 @@ public:
  */
  std::vector<COutPoint>& m_coins_to_uncache;
  const bool m_test_accept;
  + /** Disable BIP125 RBFing; disallow all conflicts with mempool transactions. */
  + const bool disallow_mempool_conflicts;
  };
  // Single transaction acceptance
  @@ -867,7 +869,8 @@ static MempoolAcceptResult AcceptToMemoryPoolWithTime(const CChainParams& chainp
  EXCLUSIVE_LOCKS_REQUIRED(cs_main)
  {
  std::vector<COutPoint> coins_to_uncache;
  - MemPoolAccept::ATMPArgs args { chainparams, nAcceptTime, bypass_limits, coins_to_uncache, test_accept };
  + MemPoolAccept::ATMPArgs args { chainparams, nAcceptTime, bypass_limits, coins_to_uncache,
  + test_accept, /* disallow_mempool_conflicts */ false };
  assert(std::addressof(::ChainstateActive()) == std::addressof(active_chainstate));
  const MempoolAcceptResult result = MemPoolAccept(pool, active_chainstate).AcceptSingleTransaction(tx, args);
  