Virtually implement __buffer__ for Python <3.12 to support typing #26783

[Andrej730]

See #26783 for the details

Note that there is also __release_buffer__ part of the buffer protocol -

numpy/numpy/__init__.pyi

Lines 2843 to 2844 in 7687245

	if sys.version_info >= (3, 12):
	def __release_buffer__(self, buffer: memoryview, /) -> None: ...

I've kept it Python 3.12+ only as it's optional part of the protocol and it's Buffer is using just __buffer__ to detect whether class supports the protocol. So, there is no need to virtually implement it for <3.12.