use mesh-builder for spacefill repr

src/apps/render-test/state.ts

src/mol-geo/primitive/box.ts

src/mol-geo/primitive/cylinder.ts

src/mol-geo/primitive/icosahedron.ts

src/mol-geo/primitive/polyhedron.ts

src/mol-geo/representation/structure/index.ts

src/mol-geo/representation/structure/spacefill.ts

src/mol-geo/shape/mesh-builder.ts

src/mol-gl/attribute.ts

src/mol-gl/renderable.ts

src/mol-gl/renderable/mesh.ts

src/mol-gl/renderable/point.ts

src/mol-gl/renderable/util.ts

src/mol-gl/renderer.ts

src/mol-gl/shader/mesh.frag

src/mol-gl/shader/point.vert