Move dpctl_ext.tensor to dpnp.tensor

[vlad-perevezentsev]

This PR proposes a refactoring that migrates dpctl_ext.tensor module into dpnp package as dpnp.tensor

Changes:

1. Moved dpctl_ext/tensor/ directory to dpnp/tensor/
2. Updated all imports from dpctl_ext.tensor to dpnp.tensor across the codebase
3. Consolidated build: removed dpctl_ext/CMakeLists.txt, added build_dpnp_tensor_ext() to dpnp/CMakeLists.txt
4. Added DPNP_BUILD_COMPONENTS CMake option (ALL/TENSOR_ONLY/SKIP_TENSOR) for staged builds
5. Split coverage workflow into two steps to avoid memory issues
6. Updated include paths in all backend extension CMake files
7. Removed dpctl_ext/ directory and cleaned up .gitignore

• 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?

[antonwolfy]

dpnp/dpnp_utils/dpnp_algo_utils.pyx still has code with dpctl.tensor usage:

    def get_array(self):
        if isinstance(self.origin_pyobj, dpctl.tensor.usm_ndarray):
            return self.origin_pyobj
        if isinstance(self.origin_pyobj, dpnp_array):
            return self.origin_pyobj.get_array()

        raise TypeError(
            "expected either dpctl.tensor.usm_ndarray or dpnp.dpnp_array.dpnp_array, got {}"
            "".format(type(self.origin_pyobj)))

[vlad-perevezentsev]

Done
Updates to error messages and comments will be included in the next PR which will update dpnp.tensor docs , error messages and comments
The current PR updated many files and addressing this kind of remarks would make the review more difficult

[antonwolfy]

still have below:

    if not isinstance(x, dpt.usm_ndarray):
        raise TypeError(f"Expected dpctl.tensor.usm_ndarray, got {type(x)}")

[antonwolfy]

needs to update below:

    if not isinstance(x, dpt.usm_ndarray):
        raise TypeError(
            "Expected `x` to be of dpctl.tensor.usm_ndarray type, got "
            f"{type(x)}"
        )

[antonwolfy]

needs to update below:

    if not isinstance(ary, dpt.usm_ndarray):
        raise TypeError(f"Expected dpctl.tensor.usm_ndarray, got {type(ary)}")

[antonwolfy]

the same dpctl.tensor usage still in many other places below

[antonwolfy]

needs to update the code below:

        # so using dpctl.tensor.vecdot instead

[ndgrigorian]

other than that minor curiosity and Anton's comments, LGTM

The base branch was changed.