Route polygons should be linked to routes

[priincee]

• [ ] switching route video should clear current polygons

• [ ] restore route polygons (if any) when starting video

  const [sourceRegions, setSourceRegions] = { "burnaby_road_stream": { "burnaby_north": { "deck_gl_features": [] }, "burnaby_south": { "deck_gl_features": [] } } };