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_input.h

@@ -10,16 +10,16 @@
 #include <optional>
 #include <string>
 #include <unordered_map>
-#include <QKeyEvent>
 #include <QKeySequence>
-#include <QSlider>
 #include <QWidget>
 #include "common/param_package.h"
 #include "core/settings.h"
 #include "input_common/main.h"
-#include "ui_configure_input.h"
 
+class QKeyEvent;
+class QLabel;
 class QPushButton;
+class QSlider;
 class QString;
 class QTimer;