[REQUEST] Add functions to query event and stream status

[shi-eric]

Description

It should be possible to query the status of an Event or Stream object to determine if all operations have completed, if the operations are still in progress (not ready), or if there is an error:

• https://docs.nvidia.com/cuda/cuda-driver-api/group__CUDA__STREAM.html#group__CUDA__STREAM_1g1b0d24bbe97fa68e4bc511fb6adfeb0b
• https://docs.nvidia.com/cuda/cuda-driver-api/group__CUDA__EVENT.html#group__CUDA__EVENT_1g6f0704d755066b0ee705749ae911deef

Context

Make it easier to diagnose issues.

[shi-eric]

This was addressed by 0eebe00.

Event.is_complete and Stream.is_complete was added to determine if the work associated with an event or stream is complete.