Fix Wayland appId

On compliant Wayland compositors windows are matched to their .desktop files by comparing the appId window property to the name of the .desktop file without the .deskop extension.

Qt5/6 by default set this property to the basename of the binary (IE `yuzu`) which does not match the expected value `org.yuzu_emu.yuzu`. We can fix this and fix window associations on compliant compositors (like Plasma) by using the `setDesktopFileName()` function which will set the appId window property. This is a no-op on X11 so is safe to be ran without guards.