Reduce or avoid GPL dependencies

[andreasnoack]

In version 2.2 a dependency on Copulas was introduced. This pulls in GSL and crlibm which are both GPL licensed. The package also has a direct dependency on FFTW which is also GPL so it would be useful to switch to AbstractFFTs or a less restrictive alternative to allow using this package in a non-GPL context.

[ChrisRackauckas]

We can make it an extension

[devmotion]

it would be useful to switch to AbstractFFTs

I quickly looked into it and it seems it would require JuliaMath/AbstractFFTs.jl#56.

[andreasnoack]

The GSL dependency in Copulas looks like it was silently removed in lrnv/Copulas.jl#73 so if the version bound here is updated the part of the issue here disappears.

[Vaibhavdixit02]

Copulas seems to have had some breaking changes in patch releases and it wasn't immediately clear to me how to fix the error in https://github.com/SciML/GlobalSensitivity.jl/actions/runs/8392054624/job/22983804323?pr=134#step:6:434 so I have opened an issue at the repo lrnv/Copulas.jl#186 will followup and create a release with the compact bounds bumped once it becomes clear how to rewrite the usage here.

[devmotion]

The GSL/Copula issue was fixed by #134, thank you @Vaibhavdixit02!

[Vaibhavdixit02]

Reopening since the FFTW issue still exists.