R1:d81d0c3ea099

Fix an issue where editing cards on a workboard with implicit column ordering could reorder cards improperly

Summary:
Depends on D20680. Ref T4900. The "BoardLayoutEngine" operates on PHIDs without knowledge of the underlying objects, but this means it has to be sensitive to PHID input order when falling back to a default layout order.

We use "default layout order" on workboards which are sorted by "Natual" order but which have one or more cards which no user has ever reordered. For example, if you add…