Move _tensor_impl extensions and use it for dpnp

[vlad-perevezentsev]

This PR proposes introducing dpctl_ext as a new internal extension module (temporarily renamed from dpctl to avoid conflicts), adding CMake/packaging support for building _tensor_impl via pybind11 and switching dpnp to use dpctl_ext.tensor. _tensor_impl

The migrated _tensor_impl currently supports the following functions:

'_array_overlap',
'_as_c_contig',
'_as_f_contig',
'_contract_iter',
'_contract_iter2',
'_contract_iter3',
'_contract_iter4',
'_copy_usm_ndarray_into_usm_ndarray',
'_ravel_multi_index',
'_same_logical_tensors',
'_unravel_index',
'default_device_bool_type',
'default_device_complex_type',
'default_device_fp_type',
'default_device_index_type',
'default_device_int_type',
'default_device_uint_type'

Files in dpnp that explicitly import dpctl.tensor._tensor_impl
Green items are handled in this PR
Red items will be handled in the next PR (#2758 )

• Have you provided a meaningful PR description?
• Have you added a test, reproducer or referred to an issue with a reproducer?
• Have you tested your changes locally for CPU and GPU devices?
• Have you made sure that new changes do not introduce compiler warnings?
• Have you checked performance impact of proposed changes?
• Have you added documentation for your changes, if necessary?
• Have you added your changes to the changelog?

[github-actions]

View rendered docs @ https://intelpython.github.io/dpnp/index.html

[github-actions]

Array API standard conformance tests for dpnp=0.20.0dev3=py313h509198e_30 ran successfully.
Passed: 1353
Failed: 4
Skipped: 7

[antonwolfy]

Please find the comments above

[ndgrigorian]

@antonwolfy already covered most thoughts I would have and more, I think this looks good