Documentation: Add doc page for dpctl.tensor._flags.Flags class

[ndgrigorian]

This PR adds a new documentation page for the Flags helper class which also lists the values its __getitem__ method will accept for dictionary-like access.

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[github-actions]

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

[coveralls]

coverage: 87.93%. remained the same
when pulling f289dd9 on document-usm-ndarray-flags-obj
into 1a789e7 on master.

[github-actions]

Array API standard conformance tests for dpctl=0.18.0dev0=py310ha798474_261 ran successfully.
Passed: 895
Failed: 0
Skipped: 119

[github-actions]

Array API standard conformance tests for dpctl=0.18.0dev0=py310ha798474_261 ran successfully.
Passed: 894
Failed: 1
Skipped: 119

[github-actions]

Array API standard conformance tests for dpctl=0.18.0dev0=py310ha798474_262 ran successfully.
Passed: 894
Failed: 1
Skipped: 119

[oleksandr-pavlyk]

Looks good to me overall with some nits

[oleksandr-pavlyk]

Perhaps the docstring of the Flags class can be rectified:

Helper class to represent memory layout flags of dpctl.tensor.usm_ndarray

Flags go beyond memory layout information now.

[ndgrigorian]

Perhaps the docstring of the Flags class can be rectified:

Helper class to represent memory layout flags of dpctl.tensor.usm_ndarray

Flags go beyond memory layout information now.

I've pushed a change to address this

[github-actions]

Array API standard conformance tests for dpctl=0.18.0dev0=py310ha798474_267 ran successfully.
Passed: 894
Failed: 1
Skipped: 119