Adding or removing multiple symbols takes O(n) time

[bhavyalatha26]

Right now we have an option only add/remove single symbol , which causes O(n) time while adding or removing 'n' symbols . This also blocks the thread and freezes the UI for that amount of time.

Instead can we have option to allow users to manage the set of symbols, circles etc (like the google_maps_flutter does) at MapboxMap level.

And whenever the set changes , the notifications are triggered and the map is updated

[m0nac0]

Support for batch adding/removing has landed with #279.