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_general.cpp

@@ -21,7 +21,7 @@ static constexpr int SettingsToSlider(int value) {
 }
 
 ConfigureGeneral::ConfigureGeneral(QWidget* parent)
-    : QWidget(parent), ui(new Ui::ConfigureGeneral) {
+    : QWidget(parent), ui(std::make_unique<Ui::ConfigureGeneral>()) {
 
     ui->setupUi(this);