duplicates for building elements within the pset_xxxcommon

Question raised by @TLiebich here https://github.com/buildingSMART/IFC4.3.x-development/issues/138#issuecomment-1013927803

> question: how do we handle similar issues of duplicates for building elements within the pset_xxxcommon?

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I also need some guidance on this topic. For example I'm working on https://forums.buildingsmart.org/t/propertysets-of-ifcspace/3997 and there the proposal is to upgrade (among others)

pset | prop
-- | --
Pset_SpaceCommon | GrossPlannedArea
Pset_SpaceCommon | NetPlannedArea

to IfcSpatialElement, which makes a lot of sense to me (most if not all can probably move from space -> spatialelement).

But to make that proposal concrete it probably means renaming Pset_SpaceCommon -> Pset_SpatialElementCommon, and changing the applicability from IfcSpace to the supertype IfcSpatialElement.

What are the backwards compatibility and inheritance ideas we have for psets like this for 4.3?