mos-xdg-env: fix XDG_DATA_DIRS and refactoring

Слиты sgakerru запросил слияние mos-xdg-env-fix в rosa2023.1

  1. Fix XDG_DATA_DIRS - now it doesn't lose /usr/local/share directory

  2. Remove kf5 directory from xdg paths. Looks like it is legacy from ALT.

  3. Refactoring script for simplification.