for unknown carbs draw polygonal prisms

src/mol-geo/primitive/prism.ts

src/mol-model/structure/structure/carbohydrates/compute.ts

src/mol-model/structure/structure/carbohydrates/constants.ts

src/mol-model/structure/structure/carbohydrates/data.ts

src/mol-repr/structure/visual/carbohydrate-symbol-mesh.ts