Convert a single pattern from a ClothAsset to a FDynamicMesh3. When PatternIndex = INDEX_NONE, convert the entire cloth asset to an FDynamicMesh3. When VertexDataType =EClothPatternVertexType::Sim3D, this generates a welded mesh (with native welded indexing) when PatternIndex = INDEX_NONE, and an unwelded (with native 2D unwelded indexing) when PatternIndex is a valid SimPatternIndex.