refactor: De-globalize g_signals

src/node/context.h

@@ -20,6 +20,7 @@ class BanMan;
 class BaseIndex;
 class CBlockPolicyEstimator;
 class CConnman;
+class CMainSignals;
 class CScheduler;
 class CTxMemPool;
 class ChainstateManager;
@@ -70,7 +71,10 @@ struct NodeContext {
     interfaces::WalletLoader* wallet_loader{nullptr};
     std::unique_ptr<CScheduler> scheduler;
     std::function<void()> rpc_interruption_point = [] {};
+    //! Issues blocking calls about sync status, errors and warnings
     std::unique_ptr<KernelNotifications> notifications;
+    //! Issues calls about blocks and transactions
+    std::unique_ptr<CMainSignals> validation_signals;
     std::atomic<int> exit_status{EXIT_SUCCESS};
 
     //! Declare default constructor and destructor that are not inline, so code