[Task] Place satellite imagery into OSM vector tile stack

[mradamcox]

Describe the task
The free tier for Mapbox's Raster Tile endpoint is much higher than the Static Tile endpoint. However, we use the Static Tile endpoint here so that we can pull in a hybrid style that has imagery as well as road labels.

Now that the OSM basemap is a vector tile style, we could use the Raster Tile endpoint and just slide the imagery layer into the map layer list underneath the existing street labels--no need to use the hybrid style from Mapbox any more.

Completion criteria
The Mapbox Raster Tile API should be used, not the Static Tile API.