Remove mempool global

src/node/context.h

@@ -35,7 +35,7 @@ class WalletClient;
 //! be used without pulling in unwanted dependencies or functionality.
 struct NodeContext {
     std::unique_ptr<CConnman> connman;
-    CTxMemPool* mempool{nullptr}; // Currently a raw pointer because the memory is not managed by this struct
+    std::unique_ptr<CTxMemPool> mempool;
     std::unique_ptr<PeerLogicValidation> peer_logic;
     ChainstateManager* chainman{nullptr}; // Currently a raw pointer because the memory is not managed by this struct
     std::unique_ptr<BanMan> banman;