Data Exchange - Step supplemental geometry support (#744)

Data Exchange - Step supplemental geometry support (#744)

- Added three new GUIDs to identify supplemental geometry containers, references, and individual supplemental geometry items in the XCAF document structure
- Implemented logic to extract and convert STEP geometric items (curves and surfaces) into TopoDS shapes when they are referenced by PMI but not present in the main model
- Refactored duplicate code for finding PMI reference positions and geometry into reusable functions