Improve coverage usmarray

[oleksandr-pavlyk]

Guided by coverage report, added tests to improve coverage.

• Have you provided a meaningful PR description?
• Have you added a test, reproducer or referred to an issue with a reproducer?
• Have you tested your changes locally for CPU and GPU devices?
• Have you made sure that new changes do not introduce compiler warnings?
• Have you checked performance impact of proposed changes?
• If this PR is a work in progress, are you opening the PR as a draft?

[github-actions]

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

[coveralls]

coverage: 91.244% (+0.2%) from 91.057%
when pulling 99172a0 on improve-coverage-usmarray
into cce23f2 on master.

[github-actions]

Array API standard conformance tests for dpctl=0.17.0dev0=py310h15de555_41 ran successfully.
Passed: 904
Failed: 2
Skipped: 94