Determine "value" or "values" recommendation

[markweitzel]

The value (singular) naming convention comes from OData. I don't think we've been consistent in Azure. I'd do an inventory of what is being used today and unless there is a clear winner/a large majority uses value, I don't have a strong opinion. We obviously wouldn't want to recommend breaking changes to "fix" the consistency problem, however.

Originally posted by @johanste in #14938 (comment)

[markweitzel]

Moved to MS Guidelines repo