Noticed while helping validate the soon to be released OpenImageIO 3.x. This cleanup makes 2 sets of changes to accommodate removed APIs [1]: - Remove `ustringHash` since it's been defined as `std::hash<ustring>` for quite some time and is fully removed in 3.0. - Replace `TypeDesc::Type*` types with just `Type*` as the former has been removed in 3.0. Cycles was using a mix of the deprecated and modern forms anyhow. [1] https://github.com/AcademySoftwareFoundation/OpenImageIO/blob/main/docs/Deprecations-3.0.md Pull Request: https://projects.blender.org/blender/blender/pulls/129136