* [ios, macos] Add the MGLLight generation templates * [ios, macos] Add MGLLight generation script * [ios, macos] Add the auto-generation script for MGLLight.mm * [ios, macos] Add the auto-generation script for MGLLightTest.mm * [core] Add const to Position constructor. * [ios, macos] Simplify MGLLightTest.mm autogenerate script.