Fix build of dpctl with sycl nightly from 2025-01-18

[oleksandr-pavlyk]

The failure was caused by TwoOffsets_FixedDimStridedIndexer not being device copyable, consequence of not being trivially copyable, consequence of using const class members contrary to C++ coding guidelines.

https://clang.llvm.org/extra/clang-tidy/checks/cppcoreguidelines/avoid-const-or-ref-data-members.html

This change adheres to the guidelines by removing const qualifier in class members.

This change also avoids unnecessary copy in constructors of fixed-dim-strided-indexers that take container arguments by values.

• 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?
• Have you added documentation for your changes, if necessary?
• Have you added your changes to the changelog?
• If this PR is a work in progress, are you opening the PR as a draft?

[oleksandr-pavlyk]

BTW, the build of main branch using latest SYCL bundle failed for this reason: https://github.com/IntelPython/dpctl/actions/runs/12848222222/job/35825346490

/home/runner/work/sycl_bundle/dpcpp_compiler/bin/../include/sycl/detail/is_device_copyable.hpp:99:17: error: static assertion failed due to requirement 'is_device_copyable_v<const dpctl::tensor::offset_utils::TwoOffsets_FixedDimStridedIndexer<1>>': The specified type is not device copyable

[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=0.19.0dev0=py310h93fe807_484 ran successfully.
Passed: 894
Failed: 2
Skipped: 118

[coveralls]

coverage: 88.18%. remained the same
when pulling f2f1221 on fix-os-llvm-build-failure
into f730de1 on master.

[ndgrigorian]

LGTM! Thank you @oleksandr-pavlyk

In a follow-up PR, I will look over our other structs and classes to eliminate const members.