DolphinQt2: Add missing Q_OBJECT macro to all QObject-related classes missing it

Without this macro, if any signals or slots were attempted to be used,
they wouldn't work; neither would various other features of the Qt
meta-object system. This can also lead to weird behavior in other
circumstances. Qt's documentation specifically states:

"Therefore, we strongly recommend that all subclasses of QObject use the
Q_OBJECT macro regardless of whether or not they actually use signals,
slots, and properties."

on its page for "The Meta-Object System", which can be seen here:
https://doc.qt.io/qt-5/metaobjects.html

Let's opt for "always do the right thing", and keep the code extensible
for the future and not have random things blow up on us.

Source/Core/DolphinQt2/QtUtils/ElidedButton.h

@@ -8,6 +8,7 @@
 
 class ElidedButton : public QPushButton
 {
+  Q_OBJECT
 public:
   explicit ElidedButton(const QString& text = QStringLiteral(""),
                         Qt::TextElideMode elide_mode = Qt::ElideRight);