Optimization in KDE Base
Save memory and time in KFileItemModel by lazy-loading the "ItemData"
To reduce unnecessary memory comsumption and CPU usage, we only fill the
QHash<QByteArray, QVariant> if the methods data(int) or setData(int) are
called for the corresponding index, or the data is necessary for sorting
According to my tests, this patch reduces the memory usage when loading
a folder with 100,000 items by 17% in Icons View, and by 26% in Details