Volume: Rename GetName to GetInternalName

This is intended to better separate it from GetNames and to clarify
that this name originally wasn't meant to be shown to users.
The ISOProperties GUI is also updated, mainly because labeling
the long banner name "short name" was confusing.

Source/Core/DiscIO/VolumeDirectory.h

@@ -40,7 +40,7 @@ public:
 	std::string GetMakerID() const override;
 
 	int GetRevision() const override { return 0; }
-	std::string GetName() const override;
+	std::string GetInternalName() const override;
 	std::map<IVolume::ELanguage, std::string> GetNames() const override;
 	void SetName(const std::string&);