The intention of this logic is to allow us to specify partial orderings
when orderings are needed (e.g. beginblock, endblock, upgrade orders),
and then have an automatic derivation of the relevant total ordering.

partialord_test.go gives a sense of how the API would look if we went with
this.

Co-authored-by: Roman <[email protected]>

Co-authored-by: Matt, Park <[email protected]>

…s into dev/partial_ordering