Fix nonzero result dtype win

[oleksandr-pavlyk]

This PR closes gh-1335.

It introduced array API notion of (device-specific) default index data type, and ensure that dpctl.tensor.nonzero
output arrays are created of this data type.

Relevant test was adjusted accordingly.

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[github-actions]

View rendered docs @ https://intelpython.github.io/dpctl/pulls/1336/index.html

[coveralls]

coverage: 84.923%. remained the same when pulling e70891b on fix-nonzero-result-dtype-win into ed93e02 on master.

[github-actions]

Array API standard conformance tests for dpctl=0.14.6dev1=py310h7bf5fec_38 ran successfully.
Passed: 912
Failed: 88
Skipped: 119

[oleksandr-pavlyk]

Verified:

(check-gh-1336) C:\Users\opavlyk>
(check-gh-1336) C:\Users\opavlyk>conda list dpctl
# packages in environment at C:\Users\opavlyk\Miniconda3\envs\check-gh-1336:
#
# Name                    Version                   Build  Channel
dpctl                     0.14.6dev1      py310h82a8827_38    file:///c:/Users/opavlyk/dpctl-channel

(check-gh-1336) C:\Users\opavlyk>python -c "import dpctl.tensor as dpt; dpt.nonzero(dpt.ones(3))"

(check-gh-1336) C:\Users\opavlyk>python -c "import dpctl.tensor as dpt; print(dpt.nonzero(dpt.ones(3)))"
(usm_ndarray([0, 1, 2]),)

(check-gh-1336) C:\Users\opavlyk>python -c "import dpctl.tensor as dpt; print(dpt.nonzero(dpt.ones(3))[0].dtype)"
int64

[vlad-perevezentsev]

LGTM!
thanks @oleksandr-pavlyk

[oleksandr-pavlyk]

The array API test failure "array_api_tests/test_special_cases.py:1240: " is marked as flaky by hypothesis, and responsible for passing tests being one fewer than in the main branch. Ready to merge.

[github-actions]

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

[github-actions]

Array API standard conformance tests for dpctl=0.14.6dev1=py310h7bf5fec_44 ran successfully.
Passed: 913
Failed: 87
Skipped: 119