Move Chebyshev functionality to Chebyshevtransforms.jl

So, I’ve rewritten the Padua transform code with extensive testing and documentation and have it registered over at ChebyshevTransforms.jl here in JuliaApproximation. I think it would make sense to transition more of the Chebyshev functionality from FastTransforms and other packages over there and then reexport here and elsewhere.

I also saw that there are multiple Julia packages doing various versions of Chebyshev polynomials. We might try to unify them here at JuliaApproximation. I might need Chebyshev polynomials for my Master’s thesis, in which case I could get started on this project.

Here are the packages I’m aware of that have functionality we might want to unify.

• FastChebInterp.jl
• ChebyshevApprox.jl
• FastTransforms.jl and ClassicalOrthogonalPolynomials.jl

It may be these packages tackle fundamentally different use cases. In any case, the future of Chebyshev transforms in Julia seems worth discussing.

Start by comparing the listed Julia packages—FastChebInterp.jl, ChebyshevApprox.jl, FastTransforms.jl, and ClassicalOrthogonalPolynomials.jl—and the existing ChebyshevTransforms.jl registration. Done requires an agreed scope for which functionality moves, how packages are unified, and where it is reexported.