f6a9f082e9
This mainly adds DNA level IDProp storage for system properties, their handling in data management code, and the forward-versioning code copying back content from system properties into 'all-in-one' single IDProperties storage, for data types that will support both in Blender 5.0. There is no user-facing changes expected here. Part of #123232. Pull Request: https://projects.blender.org/blender/blender/pulls/139257