`prelude//os/...` and `prelude//cpu/...` do not use the new constraint API

[cbarrete]

It would be nice if the prelude used the new constraint API.

I am currently cleaning up the configuration docs, and not being able to reference the new syntax is unfortunate.

Would you be open to a PR to change that? I assume that this might have some non-trivial impact on fbcode.

[8Keep]

I'm pretty sure we will get to that sometime in the first half of this year. It will likely have some internal impact.