Deprecate rapids_cpm_libcudacxx and rapids_cpm_thrust.

[bdice]

Description

Some users of Thrust have been confused about whether to use rapids_cpm_thrust or rapids_cpm_cccl. Deprecating the old CPM functions for Thrust and libcudacxx would make the messaging clearer that we intend to support primarily CCCL going forward.

It's fine if we need to extend the deprecation period for an arbitrary length of time -- but adding this notice will help push users to adopt the new CCCL monorepo.

Checklist

• [x] I am familiar with the Contributing Guidelines.
• [ ] New or existing tests cover these changes.
• [x] The documentation is up to date with these changes.
• [x] The cmake-format.json is up to date with these changes.
• [ ] I have added new files under rapids-cmake/
  • [ ] I have added include guards (include_guard(GLOBAL))
  • [ ] I have added the associated docs/ rst file and update the api.rst

[bdice]

@robertmaynard I'd appreciate your thoughts on this. I don't have a strong timeline in mind (this could slip to 24.06, or we could defer on removal for a longer time) but it would help to start communicating to users that rapids_cpm_cccl is the direction we want them to go.

[robertmaynard]

@robertmaynard I'd appreciate your thoughts on this. I don't have a strong timeline in mind (this could slip to 24.06, or we could defer on removal for a longer time) but it would help to start communicating to users that rapids_cpm_cccl is the direction we want them to go.

I agree that we need a to deprecate this for a couple of releases so that all consumers are ready for the removal. I like starting in 24.04 and yanking in 24.10

[bdice]

/merge