[ios, macos] Light property implementation in MGLStyle (#9043)
* [ios, macos] Add MGLLight to MGLStyle
* [ios, macos] Implement Objc bindings for Light object
* [ios, macos] Remove rawLight from MGLLight and re-implement it as value class
* [ios, macos] Fix build on macos
* [ios, macos] Add MGLLight documentation, Move MGLLightPosition to MGLLight
* [ios, macos] Add MGLLight tests.
* [ios, macos] Update changelogs
* [ios, macos] Fix misspelling
* [ios, macos] Fix MGLLightAnchor enum property names
* [ios, macos] Update documentation. Improve varialble naming.
* [ios, macos] Rename MGLLightPosition to MGLSphericalPosition
* [ios, macos] Update data types of MGLSphericalPosition