[FEA]: Add cuda::std::minmax

[PointKernel]

Is this a duplicate?

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Area

libcu++

Is your feature request related to a problem? Please describe.

We would like CCCL to add cuda::std::minmax, similar to how cuda::std::min and cuda::std::max correspond to std::min and std::max.
Originally posted by @bdice in rapidsai/cudf#17647 (comment)

https://godbolt.org/z/YcGEG886Y

Describe the solution you'd like

One straightforward approach is to combine the outputs of cuda::std::min and cuda::std::max.

Describe alternatives you've considered

No response

Additional context

No response

[bdice]

https://en.cppreference.com/w/cpp/algorithm/minmax

[miscco]

We already have that implemented in <cuda/std/__algorithm/minmax.h> However, it is not officially available because we do not want to ship incomplete algorithm support