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_system.cpp

@@ -228,7 +228,8 @@ static constexpr int SettingsToSlider(int value) {
     return (value - 5) / 5;
 }
 
-ConfigureSystem::ConfigureSystem(QWidget* parent) : QWidget(parent), ui(new Ui::ConfigureSystem) {
+ConfigureSystem::ConfigureSystem(QWidget* parent)
+    : QWidget(parent), ui(std::make_unique<Ui::ConfigureSystem>()) {
     ui->setupUi(this);
     connect(ui->combo_birthmonth,
             static_cast<void (QComboBox::*)(int)>(&QComboBox::currentIndexChanged), this,