ENH:s spherex-cutout method

We can and should have a new spherex specific method that calls the cutout API and also possibly deals with the WCS transformations (though that will be on the fence whether it's value added functionality or not, ideally all those transformations were happening on the server side).

cc @vandesai1 @troyraen

Begin by locating the Spherex entry point and reviewing the cutout API it should call. Resolve whether WCS transformations belong in this client or on the server, then define the method's inputs, outputs, and completion behavior before implementation.

Written by the indexing model from the issue text.