Remove obsolete dparray interface

[antonwolfy]

dpnp.dparray interface is obsolete and has not been updated for a long time. It's not assumed to be used. Instead here is dpnp.ndarray interface which is aligning with numpy.ndarray one.

The PR proposes to clean the code and to remove the obsolete interface.

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• [x] Have you tested your changes locally for CPU and GPU devices?
• [x] Have you made sure that new changes do not introduce compiler warnings?
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