Mapbox Satellite tiles should be overzoomed when not available

[ericrwolfe]

Satellite overzooming seems to be inconsistent, with areas outside of some metro areas returning empty black tiles when loading tiles z >= 18.

Example cities where overzooming works: San Francisco, Los Angeles, Austin, Mexico City, Paris, Venice.
Example cities where overzooming fails: Vancouver BC, Whistler BC, Lima Peru, Alamogordo NM, Mount Shasta CA, Truckee CA. (These same cities aren't an issue in gl-js)

A tile from an example failure area & zoom level returns a 404 and a json response:

GET https://api.mapbox.com/v4/mapbox.satellite/18/41541/[email protected]?access_token=ACCESS_TOKEN&events=true
HTTP/1.1 404 Not Found
Content-Type: application/json; charset=utf-8
{
    "message": "Tile does not exist"
}

In the major cities where overzooming does work, it seems the mapbox API does the overzooming itself:

GET https://api.mapbox.com/v4/mapbox.satellite/19/83865/[email protected]?access_token=ACCESS_TOKEN&events=true
HTTP/1.1 200 OK
Content-Type: image/jpeg

[kkaefer]

These same cities aren't an issue in gl-js

gl-js has a slightly different, but also incorrect behavior: it retains the most recent available tiles when zooming in, but doesn't actually load overzoomed lower zoom level tiles when starting out or panning into regions with no tile availability: mapbox/mapbox-gl-js#4318