Property "LoadCapacity" should be generalized

Currently, I can only find the bearing or load capacity via [LoadCapacity](https://ifc43-docs.standards.buildingsmart.org/IFC/RELEASE/IFC4x3/HTML/property/LoadCapacity.htm) in [Pset_ElementAssemblyTypeRigidFrame](https://ifc43-docs.standards.buildingsmart.org/IFC/RELEASE/IFC4x3/HTML/lexical/Pset_ElementAssemblyTypeRigidFrame.htm) and [Pset_CessBetweenRails](https://ifc43-docs.standards.buildingsmart.org/IFC/RELEASE/IFC4x3/HTML/lexical/Pset_CessBetweenRails.htm). But the concept should be more generalized to be applicable to any structural element assembly or object, not as a matter of structural analysis, but as a matter of load checks and design parameters.

Would suggest making it a property in all Pset_XxxxxCommon property sets for structural elements.

Compare the linked IFC4x3 definitions for LoadCapacity in Pset_ElementAssemblyTypeRigidFrame and Pset_CessBetweenRails, then review which structural element and object common property sets are relevant. Determine the generalized placement and scope with the specification maintainers; done means the agreed property model is reflected consistently in the applicable Pset_XxxxxCommon sets.

Written by the indexing model from the issue text.