allow `queryLayers` to be array-like

[missinglink]

This line should be rewritten in such a way that it accepts any input which is 'array-like' (ie. can be destructured with the spread operator) such that either an array or a set may be passed in.

I believe the only thing currently preventing that is the check for .size

https://github.com/pelias/spatial/blob/dec83175963fc8b632cfd97051f3f15fcbf7f975/server/routes/pip_pelias.js#L63