[ofiwg] reporting NIC attributes

[Hefty, Sean]

This is an extension of the discussion from this week's ofiwg.  Also see this PR for reference:

https://github.com/ofiwg/libfabric/pull/4443

To recap, the goal is to report device level details for domains directly associated with a NIC.

The proposal defines struct fid_nic, which references all device attributes.  That structure is returned as part of fi_getinfo() through the fi_info::handle field.  The advantage of this approach is that existing applications (like the fi_info app) would automatically display the new attributes when calling fi_tostr().  No application level changes are needed.

The issue with the proposed approach is that it is unsafe to free the attributes.  The assumption was that this could be done as part of fi_freeinfo(), but this turns out to be incorrect.

https://github.com/ofiwg/libfabric/pull/4443/files#diff-68c553057502a63de61c2506a9419d70R658

At this point, I can't think of any alternatives for reporting the device attributes that wouldn't require application level changes.  So, if you're feeling particularly clever this Friday, please feel free to make a suggestion!

- Sean