consider removing cppkokkos domain

[nmm0]

Currently we have forked the the sphinx cpp domain in a domain called cppkokkos. The idea is we wanted some specific markup for deprecated types and functions. However, we currently have a PR #451 that no one can work on for updating it to sync it with the latest sphinx release. This represents a maintenance burden for us, and will continue to cause problems in the future.

Furthermore, we can render deprecated code markings fine via C++ annotation syntax:

If this is sufficient to render (and we could hack the CSS if we wanted to change how it looked), we could entirely drop cppkokkos and reduce our maintenance burden.

Are there any other reasons why we should keep the cppkokkos domain? @fnrizzi

[fnrizzi]

There was also the use of cppkokkos to define Kokkos functions so that they are annotated with the right Kokkos macro. Since it has been a while possibly something else I am missing ... :)

[fnrizzi]

Basically we added the cppkokkos to overcome the limitations of the cpp domain Sphinx had at that time (which is a while back now) but if the regular cpp domain supports similar things now, then I agree we should go with t that

[ajpowelsnl]

@nmm0 - would you raise a PR to remove cppkokkos domain, and unfork us 😆