Retain the underlying object types when retrieving the .handle attribute

[leofang]

Today we always return a Python int and erase the type information, e.g.

cuda-python/cuda_core/cuda/core/experimental/_stream.py

Lines 140 to 143 in 61ef224

	@property
	def handle(self) -> int:
	"""Return the underlying cudaStream_t pointer address as Python int."""
	return int(self._mnff.handle)

However, it could be possible that users want to retain the underlying cuda.binding type so that it can be consumed in, say, Cython:

from cuda.core.experimental import Device

from cuda.bindings.runtime cimport cudaStream_t

s = Device().create_stream()

cdef cudaStream_t s_cy = s.handle

We should keep .handle's type, and add .ptr that returns the type-erased pointer address as Python int.

[leofang]

From #435 (comment)

FWIW I think adding ObjectCode.code (instead of Program.code) for retrieving the wrapped content makes a lot of sense. I think not having it was an overlook. Let us add it as part of #370. (ObjectCode does not have .handle, but this is close enough.)

[carterbox]

One thing that surprised me about this change is that handle() -> obj and from_handle(int) -> obj are now asymmetric, but they use the same word "handle".