[BUG - API Tiles] Examples DOWN because of unreachable hosts

[AnthonyGlt]

Some current example on iTowns website are down because the tile host failed to answer.

Context

For the example view_2d_map: It seems like c.tile.stamen.com is unreachable

For other examples (3dtiles_basic): It seems like osm.oslandia.io is unreachable

Steps to Reproduce (for bugs)

Try the examples on https://www.itowns-project.org/itowns/examples/index.html#3dtiles_basic

Actual Behavior

Possible Cause/Fix/Solution

Change our examples to request different hosts To replace osm.oslandia.io, we could use the official OSM api: https://a.tile.openstreetmap.org. It's already used in source_file_geojson_raster_2.html But should be careful that the following rules are followed: https://operations.osmfoundation.org/policies/tiles/

[AnthonyGlt]

osm.oslandia Host reachable again

[AnthonyGlt]

Concerning the example view_2d_map: The "Stamen" api changed: https://maps.stamen.com/stadia-partnership/ An account is needed and the prices are:

How much does it cost?
Once you have signed up for an account with Stadia, your cost is based on tile usage, meaning how many map tiles are requested through your app or website.

    If your current usage is less than 200,000 tiles / month—FREE for non-commercial use
    If your usage goes above 200,000 tiles / month or you are a commercial user—plans start at $20/month. The full pricing is [here](https://stadiamaps.com/pricing/).

You can reduce costs by upgrading to vector tiles. An in-depth guide to switching is available [here](https://docs.stadiamaps.com/guides/switching-your-maps-from-raster-to-vector-tiles/).

But we are using only for this example and we are using the "watercolor" and from the FAQ: If you are exclusively interested in Watercolor, the [tiles will continue to be available through the Smithsonian catalog](https://watercolormaps.collection.cooperhewitt.org/#12/40.7847/-73.9574)

I guess that for now we could use the Smithsonian catalog.

(Note: The tiles are still accessible from https://tiles.stadiamaps.com/tiles/stamen_watercolor/ but it's not in the "official process of migration" to use directly this api)

[Desplandis]

Fixed by #2246