Backport Qt patch which fixes icon loading with KDE's icon engine plugin
This change has been added to Qt 6.8.0.
Moreover, add a patch for kiconthemes which removes compatibility code
for Qt <6.8 that's not needed with the backport.
Together with a change in Kleopatra this fixes inconsistent coloring
of icons of disabled actions in high-contrast mode.
- GnuPG-bug-id: T7588