allow canvas3d creation from gl and input

src/mol-canvas3d/canvas3d.ts

src/mol-plugin/context.ts

src/tests/browser/marching-cubes.ts

src/tests/browser/render-asa.ts

src/tests/browser/render-lines.ts

src/tests/browser/render-mesh.ts

src/tests/browser/render-shape.ts

src/tests/browser/render-spheres.ts

src/tests/browser/render-structure.ts

src/tests/browser/render-text.ts