Add implementation of dpnp.ndarray.tofile method

[antonwolfy]

The PR adds implementation of dpnp.ndarray.tofile method converting the array to numpy.ndarray and calling .tofile(...) for the result.

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[github-actions]

View rendered docs @ https://intelpython.github.io/dpnp/pull/2653/index.html

[github-actions]

Array API standard conformance tests for dpnp=0.20.0dev0=py313h509198e_37 ran successfully.
Passed: 1227
Failed: 0
Skipped: 9

[coveralls]

coverage: 81.513% (+0.002%) from 81.511%
when pulling cb346fb on add-tofile-method
into 6b8ea9e on master.