baseApiUrl w/ path & normalizeTileURL functionality

[sumarlidason]

• adds regex to trim tileURL prefix to /v4/...
• adds filter to makeAPIURL preventing duplication of param 'access_token'
• adds test for edge case

closes #8458

Launch Checklist

• briefly describe the changes in this PR
• write tests for all new functionality
• document any changes to public APIs
• post benchmark scores
• manually test the debug page
• tagged @mapbox/studio and/or @mapbox/maps-design if this PR includes style spec changes
• tagged @mapbox/gl-native if this PR includes shader changes or needs a native port

[ryanhamley]

Looks good. Just need to update the description of the test

[sumarlidason]

@ryanhamley I explained this a bit in the issue; when the TileHost metadata from the api returns with a path e.g. /mbx/, the URI passed to normalizeTileURL is not formatted into a mapbox namespace tilesURL: "mapbox://tiles/..." as you see here (from an api w/o a path):

With a path the URI looks like this,

You can see that w/ the logic prior to this PR the final URL is malformed w/ duplicate /mbx and /v4.

Another possible fix for this would be to adjust whatever parses this response's resp.tiles[0] into the mapbox namespace accounting for tile hosts w/ paths (mapboxgl.baseApiUrl):

I suspect that if the URI was properly coerced to the mapbox namespace this function would continue to function w/o modifications. I am not familiar enough with mapbox-gl-js to be aware of the ramifications -

[sumarlidason]

@ryanhamley can you comment back and let me know what you think before me merge. 💯

[ryanhamley]

Yep looks good!