feat: change label placement configuration, add new 'signed area centroid' algorithm, and use new polylabel implementation (fleaflet#2102)

Co-authored-by: JaffaKetchup <[email protected]>

Author: tidu090

example/lib/misc/tile_providers.dart

@@ -4,6 +4,7 @@ import 'package:http/retry.dart';
 
 final httpClient = RetryClient(Client());
 
+// TODO: This causes unneccessary rebuilding
 TileLayer get openStreetMapTileLayer => TileLayer(
       urlTemplate: 'https://tile.openstreetmap.org/{z}/{x}/{y}.png',
       userAgentPackageName: 'dev.fleaflet.flutter_map.example',