[ios] adapt Mapbox Streets–sourced layers for user preferred language (#9582)
* [ios] Update label localization
* [ios, macos] Move MGLVectorSource+MBXAdditions.h to darwin.
* [ios, macos] Adapt Mapbox Streets to the user preferred language.
* [ios, macos] Clarify style localization documentation.
* [ios, macos] Update localization examples
* [ios, macos] Add style language reset to original.
* [ios, macos] Update changelogs.
* [ios, macos] Rename Vector Source Additions to MGL standard.
* [ios, macos] Add suport for stop localization.