Examine switching to cudarc

[juntyr]

Challenges encountered so far:

• cudarc only has the high-level DeviceSlice, no DeviceBox, though a simple wrapper around the result APIs could be written (since rust-cuda only needs it internally and doesn't expose it the memory unsafety)
• cudarc doesn't seem to have locked memory, if we would anyways switch to direct API calls this might be fine