TileRegionLoadOptions

Builds a TileRegionLoadOptions, required for TileStore.loadTileRegion(forId:loadOptions:)

averageBytesPerSecond is not a strict bandwidth limit, but only limits the average download speed. tile regions may be temporarily downloaded with higher speed, then pause downloading until the rolling average has dropped below this value.

If metadata is not a valid JSON object, then this initializer returns nil.