[release/v1] Use of `_for_coupling` suffix to indicate variables needed for coupling

[mkavulich]

We had a long discussion at a recent meeting about the use of the term "coupling" in standard names. While we did not come to a final decision, we decided that as an intermediate step, we can use a _for_coupling suffix for now, and include a detailed description of what that means.

Further consideration needs to be taken on this topic, however, as the term "coupling" is broad and ambiguous; theoretically all inter-component communication (i.e. the entire use case of Standard Names) is a kind of "coupling"! Since the reason to designate variables specifically as "for coupling" has to do with the order in which values are saved and modified, it may be best to consider dropping the term "coupling" all together in favor of "timing"/"order" suffixes.