[FEA] Add object to store curand state for reuse

[karboski]

I needed a way to store the curand state between random() calls. It's optional; the behavior of the existing API is unchanged.

It's here if you're interested:

https://github.com/karboski/MatX/tree/randomstate

[cliffburdick]

Thanks @karboski! I think random state would be a good candidate to add to our cache. We currently cache plans, stream-allocated memory, and pieces of JIT so that they can be reused. For random state this is something that is stream-oriented and could be another piece of stream state. I think it would be similar to the stream allocations where if we see the state is already allocated in a stream and can potentially be reused we can just save it off and have the random operator look it up. I will look at your code in more detail though to see if there are pieces we can use.