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()");

src/init.cpp

@@ -1229,6 +1229,17 @@ bool AppInitLockDataDirectory()
     return true;
 }
 
+bool AppInitInterfaces(NodeContext& node)
+{
+    node.chain = interfaces::MakeChain(node);
+    // Create client interfaces for wallets that are supposed to be loaded
+    // according to -wallet and -disablewallet options. This only constructs
+    // the interfaces, it doesn't load wallet data. Wallets actually get loaded
+    // when load() and start() interface methods are called below.
+    g_wallet_init_interface.Construct(node);
+    return true;
+}
+
 bool AppInitMain(const util::Ref& context, NodeContext& node, interfaces::BlockAndHeaderTipInfo* tip_info)
 {
     const ArgsManager& args = *Assert(node.args);
@@ -1318,12 +1329,6 @@ bool AppInitMain(const util::Ref& context, NodeContext& node, interfaces::BlockA
 
     GetMainSignals().RegisterBackgroundSignalScheduler(*node.scheduler);
 
-    // Create client interfaces for wallets that are supposed to be loaded
-    // according to -wallet and -disablewallet options. This only constructs
-    // the interfaces, it doesn't load wallet data. Wallets actually get loaded
-    // when load() and start() interface methods are called below.
-    g_wallet_init_interface.Construct(node);
-
     /* Register RPC commands regardless of -server setting so they will be
      * available in the GUI RPC console even if external calls are disabled.
      */

src/init.h

@@ -52,6 +52,10 @@ bool AppInitSanityChecks();
  * @pre Parameters should be parsed and config file should be read, AppInitSanityChecks should have been called.
  */
 bool AppInitLockDataDirectory();
+/**
+ * Initialize node and wallet interface pointers. Has no prerequisites or side effects besides allocating memory.
+ */
+bool AppInitInterfaces(NodeContext& node);
 /**
  * Bitcoin core main initialization.
  * @note This should only be done after daemonization. Call Shutdown() if this function fails.

src/interfaces/node.cpp

@@ -64,11 +64,10 @@ public:
     bool baseInitialize() override
     {
         return AppInitBasicSetup(gArgs) && AppInitParameterInteraction(gArgs) && AppInitSanityChecks() &&
-               AppInitLockDataDirectory();
+               AppInitLockDataDirectory() && AppInitInterfaces(*m_context);
     }
     bool appInitMain(interfaces::BlockAndHeaderTipInfo* tip_info) override
     {
-        m_context->chain = MakeChain(*m_context);
         return AppInitMain(m_context_ref, *m_context, tip_info);
     }
     void appShutdown() override