[Chapel Merge] Add a document describing how comm=ofi ensures Cha

Branch: refs/heads/master
Revision: ec660f2
Author: gbtitus
Log Message:

Merge pull request #16315 from gbtitus/ofi-README

Add a document describing how comm=ofi ensures Chapel MCM conformance.

(Reviewed by @ronawho.)

The ofi comm layer does some modestly complicated things to ensure MCM conformance,
and it has some bugs in doing so. Document all that, as a guide for near-term development
and a reference for a future developers and maintainers.

Modified Files:
A runtime/src/comm/ofi/README.md
M doc/rst/language/spec/memory-consistency-model.rst

Compare: https://github.com/chapel-lang/chapel/compare/7ba0c87ecba3...ec660f2dc03d