Minor updates dpnp.linalg.lu_factor()

[vlad-perevezentsev]

This PR suggests minor upgrades for dpnp.linalg.lu_factor() including docstring fixes, clearer warnings, improved dependency handling, adding a function to documentation generation and updating tests to use dpnp.allclose instead of assert_allclose

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• Have you made sure that new changes do not introduce compiler warnings?
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[github-actions]

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

[github-actions]

Array API standard conformance tests for dpnp=0.19.0dev3=py313h509198e_23 ran successfully.
Passed: 1227
Failed: 0
Skipped: 9

[coveralls]

coverage: 72.19% (+0.001%) from 72.189%
when pulling 4e19341 on fix_lu_factor
into 3c8ac08 on master.

[antonwolfy]

Thank you @vlad-perevezentsev