refactor: Create interfaces earlier during initialization

Add AppInitInterfaces function so wallet chain and chain client interfaces are
created earlier during initialization. This is needed in the next commit to
allow the gui splash screen to be able to register for wallet events through a
dedicated WalletClient interface instead managing wallets indirectly through
the Node interface. This only works if the wallet client interface is created
before the splash screen needs to use it.

src/bitcoind.cpp

@@ -44,7 +44,6 @@ static void WaitForShutdown(NodeContext& node)
 static bool AppInit(int argc, char* argv[])
 {
     NodeContext node;
-    node.chain = interfaces::MakeChain(node);
 
     bool fRet = false;
 
@@ -144,7 +143,7 @@ static bool AppInit(int argc, char* argv[])
             // If locking the data directory failed, exit immediately
             return false;
         }
-        fRet = AppInitMain(context, node);
+        fRet = AppInitInterfaces(node) && AppInitMain(context, node);
     }
     catch (const std::exception& e) {
         PrintExceptionContinue(&e, "AppInit()");