GPU component of CHOLMOD as package extension

[loonatick-src]

Very closely related to this issue in CUDA.jl. It was suggested that the GPU component of SuiteSparse/CHOLMOD could be implemented as a package extension to SparseArrays.jl when CUDA.jl is also available. I would like to contribute to this, but I am not sure if this (i.e. implementing as a package extension) is the right direction for this, and how exactly this would work with both SuiteSparse_jll and SuiteSparse_GPU_jll artifacts.

Would SparseArrays.jl be open for contributions pertaining to this feature?

[ViralBShah]

My understanding is that CHOLMOD does this through an environment variable, with no api change - so an extension should be easy. We have SuiteSparse_GPU_jll artifacts for this, although they perhaps need updating.

@Wimmerer Would an extension be ok?

[rayegun]

It's just an environment variable indeed. We could perhaps just add a function stub that sets and unsets this variable? And implement it in an extension.

The GPU builder, and indeed the normal one, should be updated one more time before we release 1.10.

[ViralBShah]

SS 7.2 build: JuliaPackaging/Yggdrasil#7479
SS 7.2 (GPU): JuliaPackaging/Yggdrasil#7480