Closes gh-1115, fixes docstring's Returns sections

[oleksandr-pavlyk]

Closes gh-1115 by adding Sphinx's annotations to use of usm_ndarray class to produce cross-references.

Also replaces out (usm_ndarray): with usm_ndarray: in Returns: section of docstrings. Changes are tailored to
the returned type, of course.

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[github-actions]

View rendered docs @ https://intelpython.github.io/dpctl/pulls/1140/index.html

[coveralls]

Coverage: 82.802% (-0.03%) from 82.836% when pulling d0d4bf1 on doc-clean-up-fix-gh-1115 into ede58f6 on master.

[github-actions]

Array API standard conformance tests for dpctl=0.14.3dev0=py310h76be34b_26 ran successfully.
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Failed: 788
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Array API standard conformance tests for dpctl=0.14.3dev0=py310h76be34b_27 ran successfully.
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[ndgrigorian]

For the sake of readability, it may be a good idea to either list all of the dtypes here as bullet points, or to have a page for our supported dtypes elsewhere, then redirect. The current format is a bit wordy and hard to read.

[oleksandr-pavlyk]

Yes, great suggestion. I will add a skeleton of User guide pages and make sure to include the one about supported data types. Once there, we could refer to it from docstring.

[github-actions]

Array API standard conformance tests for dpctl=0.14.3dev0=py310h76be34b_28 ran successfully.
Passed: 46
Failed: 788
Skipped: 280

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Array API standard conformance tests for dpctl=0.14.3dev0=py310h76be34b_32 ran successfully.
Passed: 46
Failed: 788
Skipped: 280

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Array API standard conformance tests for dpctl=0.14.3dev0=py310h76be34b_33 ran successfully.
Passed: 46
Failed: 788
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Array API standard conformance tests for dpctl=0.14.3dev0=py310h76be34b_34 ran successfully.
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Array API standard conformance tests for dpctl=0.14.3dev0=py310h76be34b_37 ran successfully.
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Array API standard conformance tests for dpctl=0.14.3dev0=py310h76be34b_38 ran successfully.
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Array API standard conformance tests for dpctl=0.14.3dev0=py310h76be34b_31 ran successfully.
Passed: 46
Failed: 788
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[oleksandr-pavlyk]

Thank you everybody for review. I have squashed all changes into one commit and intend to merge it shortly.

[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=0.14.3dev0=py310h76be34b_31 ran successfully.
Passed: 46
Failed: 788
Skipped: 280