Disable Plasma X11 session components by default and mark as deprecated

Neal Gomparequested to merge
ngompa/plasma-workspace:rework-x11-options into master

Reason for the change

The Plasma X11 session is deprecated starting with Plasma 6.6 and slated for removal in Plasma 6.8. Rework the X11 session options to reflect this change in affairs.

Reference: https://blogs.kde.org/2025/11/26/going-all-in-on-a-wayland-future/

Test plan

No extra work beyond apply the changes and build.

Screenshots or screen recordings

Not applicable.

Bugs fixed

Not applicable.

Merge request reports