- Remove unneeded echo and double whitespace

- Remove patches used as sources and replace them with direct
ln -s and sed commands:
* lookandfeel.diff, sddmtheme.diff, lookandfeel_jpg.diff,
sddmtheme_jpg.diff
- Use %require_ge for wallpaper-branding-openSUSE

- Use lookandfeel_jpg.diff and sddmtheme_jpg.diff on Leap <=15.5
TW and Leap 15.6+ use png for the default wallpaper

- Modify lookandfeel.diff and sddmtheme.diff to support
branding-openSUSE 84.87.20240405 which replaces jpg wallpapers
with png ones.
- Require at least wallpaper-branding-openSUSE 84.87.20240405
to make sure the png wallpapers exist.