experimental: remove x86 modules

The modules were ported from an older config, unknown if needed.
site-ffda (Darmstadt) seems not not use them, or have any mention of
them. Additionally, we do not currently have any x86 devices in the
network.

Removal of legacy info makes the config easier to grasp.

experimental: v2023.2.5 for 2025_08_22

This update required bigger changes: moving information from "site.mk"
to a new file called "image-customization.lua".

I do not like the x86-specific packages, but I kept them as nobody told
me if they were needed or not.