Refactor MGLMapSnapshotter attribution

[1ec5]

As followup from #10456, MGLMapSnapshotter’s attribution logic is inflexible and needs to be refactored:

• MGLSnapshotAttributionOptions goes away.
• An MGLAttributionInfoStyle enumeration along the lines of NSFormattingUnitStyle or NSDateFormatterStyle. “Short” for a logo means just the helmet; “short” for an attribution item could mean abbreviation.
• -[MGLMapSnapshotter logoImageWithStyle:] returns either the full image or the helmet image.
• -[MGLAttributionInfo sizeWithStyle:] determines the size of an individual attribution image, depending on whether it’s abbreviated or written out in full.
• -[MGLMapSnapshotter attributionSizeWithLogoStyle:sourceAttributionStyle:] takes two MGLAttributionInfoStyles and returns the size of the attribution.
• The snapshot completion handler tries calling -[MGLMapSnapshotter attributionSizeWithLogoStyle:sourceAttributionStyle:] with each permutation of attribution info styles. Once one of the permutations fits the snapshot’s width, it uses -[MGLMapSnapshotter logoImageWithStyle:] and MGLAttributionInfo to put together the attribution.

/cc @fabian-guerra @lilykaiser

[fabian-guerra]

Fixed in #10525