Change MapStyle

[hactar]

Because we only set the mapStyle during makeUIView, a later change to the styleURL parameter does nothing. This PR adds a check to updateUIView to see if the styleURL changed, and if yes, sets the new URL on the mapView, allowing users to change the mapStyle at runtime (for example to change from a vector to a satellite map style).

[ianthetechie]

heh... very good catch. I thought I had handled this correctly, but it turns out I was doing a trivially true comparison in the method that actually does the heavy lifting. I'll make some edits + document what's going on better.

[ianthetechie]

cc @Archdoog I actually found an even better approach after our quick review that's robust to any future style types we introduce. Part of the original reason that this lived in the coordinator was to take advantage of the snapshotting, so I've used that to ensure against unnecessary updates (sometimes the underlying native implementations do dumb things so it's best to just not ask them to change stuff that isn't changed).