feat: Assign java max mem based on system RAM

If the system has <6GB RAM, it uses (system RAM / 1.5)
If the system has >=6GB, it uses 4GB

Signed-off-by: txtsd <code@ihavea.quest>

launcher/Application.h

@@ -198,6 +198,8 @@ public:
 
     void ShowGlobalSettings(class QWidget * parent, QString open_page = QString());
 
+    int suitableMaxMem();
+
 signals:
     void updateAllowedChanged(bool status);
     void globalSettingsAboutToOpen();