[FEATURE REQUEST] Implement Stream priorities

[hyperfraise]

I think I'm able to say that stream priority isn't implemented in pycuda right now.

Although Cuda gives the possibility to allocate priorities to Streams, as pointed out here :
https://docs.nvidia.com/cuda/cuda-c-programming-guide/index.html#stream-priorities

Will you please think about adding this feature whenever you can ? Or do you know of any workaround ?

Cordially

[inducer]

This seems simple to implement, but it's unlikely I'll have the spare bandwidth for it soon. I'm happy to look at PRs though.

[hyperfraise]

@inducer I went ahead and did it. Can you check please ?