Add complex numbers

[opfromthestart]

Closes #821.
I had to use a proxy object to implement cuda traits. It built with cargo build -F complex,cuda,nightly,f16

[chelsea0x3b]

We can add these to cudarc in a PR there behind a feature flag, that should allow us to not need the wrapper type, right?

[opfromthestart]

I was unaware that you controlled cudarc. That would work yes.

[chelsea0x3b]

How does this interact with cuda kernels?

[opfromthestart]

I don't think it would work at all with cuda kernels atm. Not familiar with how cuda types work, can you overload operators for a custom complex struct?

[chelsea0x3b]

I don't think it would work at all with cuda kernels atm. Not familiar with how cuda types work, can you overload operators for a custom complex struct?

We could potentially just merge this for Cpu and make sure we get compile errors for cuda.

You can overload operators in c++, but I'm not sure that's sufficient to make the kernels work in the same way as they do in rust land.