Add managed-memory advise, prefetch, and discard-prefetch on Buffer

[rparolin]

Summary

Add managed-memory range controls to cuda.core.Buffer:

• Buffer.advise(...)
• Buffer.prefetch(...)
• Buffer.discard_prefetch(...)

This addresses #1332.

Details

These operations are implemented on Buffer because the CUDA driver APIs apply to a memory range, not specifically to
ManagedMemoryResource. That allows the new methods to work for both:

• buffers allocated from ManagedMemoryResource
• externally wrapped managed allocations

The implementation adds managed-memory detection for buffers, normalizes device/host/NUMA location inputs, and forwards to the existing
driver bindings for cuMemAdvise, cuMemPrefetchAsync, and cuMemDiscardAndPrefetchBatchAsync.

Tests

Adds coverage for:

• advise/prefetch/discard-prefetch on managed-memory buffers
• support for externally wrapped managed allocations
• rejection on non-managed buffers
• invalid input combinations
• observable driver-side effects via cuMemRangeGetAttribute(...)

Closes #1332

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[rparolin]

/ok to test

[jrhemstad]

question: Does making these member functions of the Buffer type preclude this functionality for allocations that weren't created through the Buffer type? Did we consider making these free functions instead of member functions on the Buffer type?

[rparolin]

question: Does making these member functions of the Buffer type preclude this functionality for allocations that weren't created through the Buffer type? Did we consider making these free functions instead of member functions on the Buffer type?

I'm moving this back into draft. We discussed in our team meeting because I was already hesitant as Buffer is becoming a 'God object' with the functionality is gaining. We were going to explore alternatives. Free functions sounds like a good alternative to explore.