cuda.core: account for DLTensor.byte_offset in from_dlpack

[fedonman]

Description

closes #2592

DLPack places a tensor's first element at data + byte_offset. view_as_dlpack, which backs StridedMemoryView.from_dlpack and from_any_interface, set ptr from data alone, so a producer that reports the allocation base in data and expresses a slice as byte_offset produced a view pointing byte_offset bytes before the tensor, with nothing raised. The capsule-consuming importer in the same module, _smv_from_dlpack_capsule, already folds byte_offset in, so the two import paths disagreed about the same capsule. This makes view_as_dlpack match it, and that one line is the whole production change.

Correcting ptr also fixes the round-trip. The __dlpack__ re-export writes ptr back out as data with byte_offset = 0, so before this change a non-zero offset was dropped permanently on the way back out.

The new test exercises both the versioned and the unversioned capsule branches. It views the first 8 elements of a 9-element array, then re-describes the same tensor as src[1:9] by writing byte_offset alone, so a regression fails an assertion rather than reading out of bounds. shape and strides share a single producer-owned allocation, so the test does not touch them.

A release note is added under Fixes and enhancements in cuda_core/docs/source/release/1.2.0-notes.rst; the affected behavior has been present since 0.1.0.

Verification

The new test, both capsule flavours:

tests/test_utils_dlpack.py::test_from_dlpack_honours_byte_offset[unversioned] PASSED [ 50%]
tests/test_utils_dlpack.py::test_from_dlpack_honours_byte_offset[versioned] PASSED [100%]
======================= 2 passed, 30 deselected in 0.11s =======================

The same test with the one-line change reverted:

=========================== short test summary info ============================
FAILED tests/test_utils_dlpack.py::test_from_dlpack_honours_byte_offset[unversioned]
FAILED tests/test_utils_dlpack.py::test_from_dlpack_honours_byte_offset[versioned]
======================= 2 failed, 30 deselected in 0.14s =======================

The full cuda_core suite:

3569 passed, 412 skipped, 1 xfailed in 159.90s (0:02:39)

Checklist

• New or existing tests cover these changes.
• The documentation is up to date with these changes.

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