Add SYCL backend for AssmbScatr and add generalized atomic function to LoopExecution

Issue/feature addressed

This MR update the redesign to allow the future implementation of a SYCL backend for the FwdTrans and the HelmSolve operators.

• Add a SYCL backend for the AssmbScatr operators
• Tidy-up LoopExecution
• Add generalized atomic function wrapper for CUDA, SYCL, and Kokkos
• Add SYCL math profiler
• Update ConjGrad for the SYCL backend
• Fix workspace memory allocation for BwdTrans, IProductWRTBase, and IProductWRTDeriveBase

Proposed solution

Implementation

Tests

Suggested reviewers

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Notes

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Checklist

• Functions and classes, or changes to them, are documented.
• [ ] User guide/documentation is updated.
• [ ] Changelog is updated.
• Suitable tests added for new functionality.
• Contributed code is correctly formatted. (See the contributing guidelines).
• License added to any new files.
• No extraneous files have been added (e.g. compiler output or test data files).