Items that are blocking the registration of StrideArrays in the General registry

[DilumAluthge]

1. Remove threading utils and depend on ThreadingUtilities.jl (#1)
2. Remove matmul code and depend on Octavian.jl

Anything else that needs to be done before we register StrideArrays?

[chriselrod]

That about sums it up.

Would be nice to have documentation and benchmarks, and matmul benchmarks hosted at Octavian.jl to reference w/ respect to that.

I think I'd also like to add a dependency on RecursiveFactorization, to make this a bit of an ArrayInterface and Julia BLAS-and-LAPACK be default library (but only if they're at least as fast as alternatives for <= 200x200 arrays).

[DilumAluthge]

Looks like both number 1 and number 2 are done?

What do you think about registering an initial version now?

[chriselrod]

Done.