[FEA]: Support inheritance from Buffer

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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

Beginne damit, cuda.core's Buffer-Implementierung und die Methoden from_handle() und _reduce_helper() zu lokalisieren, und untersuche anschließend, wie zurückgegebene Instanzen erstellt werden. Prüfe das zugehörige Issue #750 und das relevante Verhalten von Buffer; abgeschlossen ist die Arbeit, wenn Unterklassen beide Methoden erben und Instanzen der Unterklasse erhalten, ohne das bestehende Verhalten von Buffer zu beeinträchtigen.