Implements dpctl.tensor.nextafter per array API

[ndgrigorian]

This PR implements the nextafter function coming to the next version of the array API specification

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[github-actions]

Deleted rendered PR docs from intelpython.github.com/dpctl, latest should be updated shortly. 🤞

[coveralls]

coverage: 87.97% (+0.003%) from 87.967%
when pulling e5f9810 on dpctl-tensor-nextafter
into f646ac1 on master.

[github-actions]

Array API standard conformance tests for dpctl=0.18.0dev0=py310h15de555_105 ran successfully.
Passed: 894
Failed: 15
Skipped: 105

[github-actions]

Array API standard conformance tests for dpctl=0.18.0dev0=py310h15de555_113 ran successfully.
Passed: 894
Failed: 15
Skipped: 105

[oleksandr-pavlyk]

LGTM! Thank you @ndgrigorian

I did push changes to extend test file.

[oleksandr-pavlyk]

BTW, test_nextafter_special_cases_zero[f2] fails for CUDA devices:

In [1]: import dpctl.tensor as dpt

In [2]: x1 = dpt.asarray([-0.0, 0.0, -0.0, 0.0], dtype="f2", device="cuda")

In [3]: x2 = dpt.asarray([0.0, -0.0, -0.0, 0.0], dtype="f2", device="cuda")

In [4]: dpt.nextafter(x1, x2)
Out[4]: usm_ndarray([-0.,  0., -0.,  0.], dtype=float16)

In [5]: y1 = dpt.asarray([-0.0, 0.0, -0.0, 0.0], dtype="f2")

In [6]: y2 = dpt.asarray([0.0, -0.0, -0.0, 0.0], dtype="f2")

In [7]: dpt.nextafter(y1, y2)
Out[7]: usm_ndarray([ 0., -0., -0.,  0.], dtype=float16)

[oleksandr-pavlyk]

Reported as OFNAAO-302. Will add skipping this test for "float16" on CUDA devices for now.

[github-actions]

Array API standard conformance tests for dpctl=0.18.0dev0=py310h15de555_116 ran successfully.
Passed: 894
Failed: 15
Skipped: 105

[antonwolfy]

I've reused it in dpnp-1938 and it works fine. Thank you!