Disable Codex docs build for now to avoid OOM issue

The build process for the Codex docs runs out of memory. The docs are not that important for patchdemo, so rather than trying to increase the amount of available memory, just disable the docs build for now.

Also copy files for the design tokens package, and update the list of files that is copied for the icons package.

This is a bit messy, but hopefully we can make all of this code obsolete in the future by implementing T314507.