Contribution to fix gh 1887

[oleksandr-pavlyk]

This PR contributes to gh-1890, by streamlining code for performing copy to contiguous array.

1. Save common subexpressions to variables

2. Sub-group size type changed to uint16 (from uint32)

3. sg.get_local_range() replaced with sg.get_max_local_range()

   This is safe to do since work-group size is chosen to be a multiple of sub-group size for all possile choices of sub-group size (1, 8, 16, 32, 64)

4. Simplified computation of base value in generic branch for complex types, or when sg_load is disabled, to avoid a division (and left a comment)

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• [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?
• [x] Have you checked performance impact of proposed changes?
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• [ ] Have you added your changes to the changelog?
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[github-actions[bot]]

View rendered docs @ https://intelpython.github.io/dpctl/pulls/1891/index.html

[github-actions[bot]]

Array API standard conformance tests for dpctl=0.19.0dev0=py310hdf72452_201 ran successfully. Passed: 895 Failed: 0 Skipped: 119

[github-actions[bot]]

Array API standard conformance tests for dpctl=0.19.0dev0=py310hdf72452_202 ran successfully. Passed: 894 Failed: 1 Skipped: 119