Update context attribute query

[nsarka]

From the UCC Backlog:

Check all TLs and CLs lib and context attributes

Attribute query function should follow this scheme:
if attr.mask is not zero check each attributed defined in mask
Set attribute according to Tl/CL capabilities
Set attr.flags always

This logic is generally broker in UCC, for example
ucc_tl_self_get_context_attr(const ucc_base_context_t *context, /* NOLINT */
                             ucc_base_ctx_attr_t      *attr)
{
    return UCC_OK;
}

attr.topo_required is not set (returns something random)
attr.global_work_buffer_size is not set
etc.

This PR updates UCC so that all context attribute queries read the mask for each field and then write a value, usually 0. Some of these were missing.

The backlog task mentions updating lib attributes as well, but it seems to me that both CL and TL lib attributes are filled correctly. There are two unused fields not filled--reduction types and sync type--but if the mask has these bits set UCC will error before it reaches the CL or TL (see ucc_lib_get_attr).

[janjust]

@nsarka IMO, I think an easier to read and understand approach is to simply define a zero_attr() function that will zero out the attributes prior to going over the mask bit and setting everything as needed.
Rather than going through all the bitmask fields and individually zero everything out

[nsarka]

@nsarka IMO, I think an easier to read and understand approach is to simply define a zero_attr() function that will zero out the attributes prior to going over the mask bit and setting everything as needed. Rather than going through all the bitmask fields and individually zero everything out

Updated

[janjust]

@nsarka please squash commits and rebase

[janjust]

Looks good to me, but I just have to caution that the user must know, either through documentation or otherwise that the attr is in fact cleared and set to only masked values

[samnordmann]

LGTM! Please update copyrights

[nsarka]

Copyright updated and commits squashed!