Merge bitcoin/bitcoin#30393: refactor: use existing RNG object in ProcessGetBlockData

fa2e74879a net_processing: use existing RNG object in ProcessGetBlockData (MarcoFalke)

Pull request description:

  Small follow-up to commit 8e31cf9c9b

ACKs for top commit:
  dergoegge:
    Code review ACK fa2e74879a
  glozow:
    ACK fa2e74879a

Tree-SHA512: 12709c79e6eefad184609b7306e0f65cb00123e39636cf8b7d538feb25c05ba3c36aa41468886c904a5f44fea267e67f9c4fbbab8733753d1c891b90fa40ce8b

src/net_processing.cpp

@@ -1096,7 +1096,7 @@ private:
     bool BlockRequestAllowed(const CBlockIndex* pindex) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
     bool AlreadyHaveBlock(const uint256& block_hash) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
     void ProcessGetBlockData(CNode& pfrom, Peer& peer, const CInv& inv)
-        EXCLUSIVE_LOCKS_REQUIRED(!m_most_recent_block_mutex);
+        EXCLUSIVE_LOCKS_REQUIRED(g_msgproc_mutex, !m_most_recent_block_mutex);
 
     /**
      * Validation logic for compact filters request handling.
@@ -2522,7 +2522,7 @@ void PeerManagerImpl::ProcessGetBlockData(CNode& pfrom, Peer& peer, const CInv&
                 if (a_recent_compact_block && a_recent_compact_block->header.GetHash() == pindex->GetBlockHash()) {
                     MakeAndPushMessage(pfrom, NetMsgType::CMPCTBLOCK, *a_recent_compact_block);
                 } else {
-                    CBlockHeaderAndShortTxIDs cmpctblock{*pblock, FastRandomContext().rand64()};
+                    CBlockHeaderAndShortTxIDs cmpctblock{*pblock, m_rng.rand64()};
                     MakeAndPushMessage(pfrom, NetMsgType::CMPCTBLOCK, cmpctblock);
                 }
             } else {