iOS/macOS reusable snapshotter

[fabian-guerra]

The current status of MBGLSnapshotter does not allow full reuse.

In a chat with @frederoni he confirmed:

It can be reused but the associated MGLMapCamera is transformed to mbgl::CameraOptions upon initializing so pretty much every case you want to reuse it won’t work.

Imagine using a snapshotter when you scroll through a table view.

• cellWillDisappear/prepareForReuse should cancel the snapshotter
• but you can’t reuse because the camera is already set. (you can reuse but the region will most likely not be the same)

In order to make it reusable it will require move MGLMapSnapshotOptions to a setter which is an easy task.
The questions would be if it's valuable for developers have a reusable snapshotter and which would be the uses cases for it.

/cc @1ec5 @frederoni @boundsj