Step 4 of T349423:

Turn the @wikimedia/codex RL module into a collector module

We would like to pursue a more elaborate version of this that would allow loading this module to still load the whole library, but that's pending feedback from the MW team. In the meantime, we can implement the simple version, where we remove the current contents of this module and replace it with something that collects and exposes loaded components.

This would break existing code, so it could not be merged until we either figure out a way to do the more elaborate version, or figure out a way to migrate existing code (perhaps by introducing a new codex-all module or something).