Use OOP for surface integrals with faster methods for tensor product grids

[dpanici]

https://github.com/PlasmaControl/DESC/blob/95612fa625bd5ba939569004c767ed02594586f0/desc/integrals/surface_integral.py#L11

either their own classes, or as methods of grid classes

[unalmis]

So just for computing stuff, e.g. obj.compute, exactly 25% of the total computation time is spent on doing these surface integrals. They require an FFTable grid anyway, so using the faster tensor product methods for these integrals would be a nice performance gain.