Possible regression in handling of special style names

This has not been verified yet, but from looking at the code, there is a possible regression caused by https://codereview.qt-project.org/c/qt/qtbase/+/625610

If two fonts in the same family have identical properties but different style names, then these will no longer be regarded as two different fonts, causing only the last one to be accessible from the application.

This should be tested and fixed if it is a correct analysis.