[EPIC]: mdspan-based algorithms

[fbusato]

Is this a duplicate?

• I confirmed there appear to be no duplicate issues for this request and that I agree to the Code of Conduct

Area

libcu++

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

1. mdspan represents the C++ abstraction for multidimensional data. We currently support only a small subset of available features
2. The llm.c version presented to the CUDA MODE group can be greatly simplified and improved by supporting additional features related to mdspan

Describe the solution you'd like

• Provide a cuda:: streaming accessor instead of manually instantiate it
• Allow mdspan to support device-only/host-only code for custom accessors and layouts
• Provide for_each_in_extent to directly linearization/de-linearization multidimensional indices
• Provide mdarray (owning version of mdspan)
• Provide a vocabulary type to declare host or device mdspan/mdarray

Describe alternatives you've considered

No response

Additional context

No response