yuzu: Fixes to game list sorting

Should fix citra-emu/citra#4593.
As the issue might not be entirely clear, I'll offer a short explanation from what I understood from it and found from experimentation.

Currently yuzu offers the user the option to change the text that's displayed in the "Name" column in the game list. Generally, it is expected that the items are sorted based on the displayed text, but yuzu would sort them by title instead.

Made it so that an access to SortRole returns the same as DisplayRole.
There shouldn't be any UI changes, only change in behaviour.

Also fixes a bug with directory sorting, where having the directories out of order would enable you to try to "move up" to the addDirectory button, which would crash the emulator.

Co-Authored-By: Vitor K <vitor-k@users.noreply.github.com>