Use unique_ptr on all ui objects from .ui files (#5511)

* Forward declare ui and use unique_ptr

* ConfigureEnhancements: use unique_ptr for ui

* Use make_unique instead of new where applicable

* Move some of the ui includes that already used unique_ptr

* main.cpp: also make use of make_unique on Config

* Address review comments

src/citra_qt/configuration/configure_enhancements.h

@@ -4,6 +4,7 @@
 
 #pragma once
 
+#include <memory>
 #include <QWidget>
 
 namespace Settings {
@@ -29,6 +30,6 @@ private:
     void updateShaders(Settings::StereoRenderOption stereo_option);
     void updateTextureFilter(int index);
 
-    Ui::ConfigureEnhancements* ui;
+    std::unique_ptr<Ui::ConfigureEnhancements> ui;
     QColor bg_color;
 };