Fix undefined behavior in integer advanced indexing and indexing functions

[ndgrigorian]

This PR proposes a solution to undefined behavior that could occur in some edge cases with integer advanced indexing, where indices OOB for ssize_t (aka std::ptrdiff_t) would be cast directly to ssize_t and overflow or underflow.

As ssize_t/std::ptrdiff_t is defined to be a signed type with the same size as size_t, this means that on 32-bit systems, overflow/underflow could occur for even smaller values.

This PR also re-organizes integer_advanced_indexing.hpp by reducing namespace clutter, and moves the rewritten ClipIndex and WrapIndex structs into a separate header file. This enables them to be re-used more easily in extensions.

• [X] Have you provided a meaningful PR description?
• [x] Have you added a test, reproducer or referred to an issue with a reproducer?
• [X] Have you tested your changes locally for CPU and GPU devices?
• [X] Have you made sure that new changes do not introduce compiler warnings?
• [ ] Have you checked performance impact of proposed changes?
• [ ] Have you added documentation for your changes, if necessary?
• [x] Have you added your changes to the changelog?
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[github-actions[bot]]

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

[github-actions[bot]]

Array API standard conformance tests for dpctl=0.19.0dev0=py310hdf72452_209 ran successfully. Passed: 894 Failed: 1 Skipped: 119

[coveralls]

coverage: 87.705%. remained the same when pulling ba0bfd90bd06ee3d9de568bc415efa9f7b950743 on fix-indexing-oob-indices into dd2812f4d5d06c565a1258af94a1378ba1759c1e on master.

[github-actions[bot]]

Array API standard conformance tests for dpctl=0.19.0dev0=py310hdf72452_212 ran successfully. Passed: 894 Failed: 1 Skipped: 119