qt: Fix -Wsfinae-incomplete warnings when building with GCC 16.x

According to the CMake documentation for `AUTOMOC`, all `moc` output
files that are not included in a source file are aggregated into the
CMake-generated `<AUTOGEN_BUILD_DIR>/mocs_compilation.cpp`, which is
added to the target's sources.

Within that single translation unit, `moc`-generated code checks the
completeness of a signal or slot parameter type while it is still only
forward-declared, and the type is completed later, when a subsequently
included `moc_*.cpp` file pulls in the header that defines it. GCC 16.x
diagnoses this pattern with the `-Wsfinae-incomplete` warning, which is
enabled by default.

Including the `moc` output files at the end of the corresponding source
files excludes them from `mocs_compilation.cpp`, so each one is
compiled in a translation unit where the relevant types are complete.

Additionally:
1. Some of the `BitcoinGUI` class's private members are gated with
   `#ifdef ENABLE_WALLET` to prevent `-Wunused-private-field` warnings
   when building with `-DENABLE_WALLET=OFF`.
2. `test/lint/lint-includes.py` is adjusted to allow new `#include`
   statements.

src/qt/bitcoingui.cpp

@@ -1721,3 +1721,5 @@ void UnitDisplayStatusBarControl::onMenuSelection(QAction* action)
         optionsModel->setDisplayUnit(action->data());
     }
 }
+
+#include <moc_bitcoingui.cpp>

src/qt/bitcoingui.h

@@ -114,7 +114,9 @@ protected:
 
 private:
     interfaces::Node& m_node;
+#ifdef ENABLE_WALLET
     WalletController* m_wallet_controller{nullptr};
+#endif // ENABLE_WALLET
     std::unique_ptr<interfaces::Handler> m_handler_message_box;
     std::unique_ptr<interfaces::Handler> m_handler_question;
     ClientModel* clientModel = nullptr;
@@ -158,15 +160,17 @@ private:
     QAction* m_restore_wallet_action{nullptr};
     QAction* m_close_wallet_action{nullptr};
     QAction* m_close_all_wallets_action{nullptr};
+#ifdef ENABLE_WALLET
     QAction* m_wallet_selector_label_action = nullptr;
     QAction* m_wallet_selector_action = nullptr;
+#endif // ENABLE_WALLET
     QAction* m_mask_values_action{nullptr};
     QAction* m_migrate_wallet_action{nullptr};
     QMenu* m_migrate_wallet_menu{nullptr};
-
+#ifdef ENABLE_WALLET
     QLabel *m_wallet_selector_label = nullptr;
     QComboBox* m_wallet_selector = nullptr;
-
+#endif // ENABLE_WALLET
     QSystemTrayIcon* trayIcon = nullptr;
     const std::unique_ptr<QMenu> trayIconMenu;
     Notificator* notificator = nullptr;

src/qt/qvalidatedlineedit.cpp

@@ -126,3 +126,5 @@ bool QValidatedLineEdit::isValid()
 
     return valid;
 }
+
+#include <moc_qvalidatedlineedit.cpp>

src/qt/sendcoinsentry.cpp

@@ -238,3 +238,5 @@ bool SendCoinsEntry::updateLabel(const QString &address)
 
     return false;
 }
+
+#include <moc_sendcoinsentry.cpp>

test/lint/lint-includes.py

@@ -70,7 +70,11 @@ def find_included_cpps():
         if e.returncode > 1:
             raise e
 
-    return included_cpps
+    # Exception: `#include <moc_*.cpp>` statements in src/qt source files are permitted.
+    # See:
+    # - https://doc.qt.io/qt-6/moc.html
+    # - https://cmake.org/cmake/help/latest/prop_tgt/AUTOMOC.html
+    return [i for i in included_cpps if not re.match(r"src/qt/[^:]+\.cpp:#include <moc_[^<>:]+\.cpp>$", i)]
 
 
 def find_extra_boosts():