DolphinQt: Move common controller interface logic to its own widget

Source/Core/DolphinQt/Config/CommonControllersWidget.h

@@ -0,0 +1,35 @@
+// Copyright 2021 Dolphin Emulator Project
+// Licensed under GPLv2+
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include <QWidget>
+
+#include <array>
+
+class QCheckBox;
+class QGroupBox;
+class QVBoxLayout;
+class QPushButton;
+
+class CommonControllersWidget final : public QWidget
+{
+  Q_OBJECT
+public:
+  explicit CommonControllersWidget(QWidget* parent);
+
+private:
+  void OnControllerInterfaceConfigure();
+
+  void CreateLayout();
+  void ConnectWidgets();
+
+  void LoadSettings();
+  void SaveSettings();
+
+  QGroupBox* m_common_box;
+  QVBoxLayout* m_common_layout;
+  QCheckBox* m_common_bg_input;
+  QPushButton* m_common_configure_controller_interface;
+};