Move dpctl_ext.tensor to dpnp.tensor

[vlad-perevezentsev]

TBA

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• Have you made sure that new changes do not introduce compiler warnings?
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• Have you added your changes to the changelog?

[github-actions]

View rendered docs @ https://intelpython.github.io/dpnp/pull/2829/index.html

[github-actions]

Array API standard conformance tests for dpnp=0.20.0dev3=py313h509198e_303 ran successfully.
Passed: 1356
Failed: 1
Skipped: 16