[FEA]: Support inheritance from Buffer

Is this a duplicate?

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Area

cuda.core

Is your feature request related to a problem? Please describe.

nvmath-python is considering creating a subclass of Buffer specific to NVSHMEM because we want to mostly follow cuda.core's semantics for Buffer/MemoryResource, but need some different behavior regarding garbage collection.

Describe the solution you'd like

Buffer should use classmethod instead of staticmethod for all methods that return an instance of the class. i.e. from_handle() and _reduce_helper()

Describe alternatives you've considered

Composing Buffer with our Buffer.
Replicating the Buffer protocol with an unrelated class.
Rolling our own MemoryResource/Buffer abstraction that is unique to nvmath's distributed APIs.

Additional context

Related to: https://github.com/NVIDIA/cuda-python/issues/750

Start by locating cuda.core's Buffer implementation and its from_handle() and _reduce_helper() methods, then inspect how returned instances are constructed. Review the related issue #750 and relevant Buffer behavior; done when subclasses inherit both methods and receive subclass instances without breaking existing Buffer behavior.