mhp ISHMEM integration

[lslusarczyk]

Summary

ISHMEM based multi process communication primitives as a backend for Distributed-Ranges.

Feature details

This is direct continuation of #631 feature. The feature here just provides additional support for:

• distributed_mdarray
• algorithms: for_each_tile, reduce, sort, inclusive_scan, exclusive_scan,
• Distributed Range Views: zip, iota
• Distributed Mdspan Algorithms: mdfor_each, mdfor_each_stencil, mdfor_each_tile

This feature here also adds communication primitives for:

• implementing distributed mdspan remote reference, which is exposed as (index0, index1, ...)
• halo exchange in distributed_mdarray

References

• mhp basic ISHMEM integration #631 feature
• wiki about integration
• ISHMEM documentation