Align CUDA sources with C++17

[JensWehner]

GauXC’s CUDA sources are not strictly C++14-compatible because they already use C++17 features such as if constexpr. However, the build configuration declares cuda_std_14, while several kernels still use the register keyword, which was removed in C++17.

This PR aligns the declared CUDA standard with the code by:

Changing cuda_std_14 to cuda_std_17.
Removing obsolete register qualifiers that Clang diagnoses in C++17 mode.

[awvwgk]

Thanks for making this consistent across the codebase.

[Copilot]

🟢 Approval recommended

The standard declarations now match existing language usage, and all obsolete CUDA register occurrences were removed without changing kernel behavior.

Pull request overview

Aligns CUDA compilation with existing C++17 usage while removing obsolete register qualifiers.

Changes:

• Sets active and archived CUDA targets to cuda_std_17.
• Removes register from affected CUDA kernel locals.

File summaries

File	Description
src/xc_integrator/local_work_driver/device/cuda/kernels/uvvars_mgga.hpp	Removes obsolete qualifiers from MGGA locals.
src/xc_integrator/local_work_driver/device/cuda/kernels/uvvars_lda.hpp	Removes the LDA qualifier.
src/xc_integrator/local_work_driver/device/cuda/kernels/uvvars_gga.hpp	Removes GGA local qualifiers.
src/xc_integrator/local_work_driver/device/cuda/kernels/grid_to_center.cu	Updates the coordinate local declaration.
src/runtime_environment/device/cuda/CMakeLists.txt	Requires CUDA C++17.
attic/src/new_integrator/device/cuda/gauxc-cuda.cmake	Updates archived CUDA standard.
attic/src/new_integrator/device/cuda/cuda_weights.cu	Removes an archived coordinate qualifier.
attic/src/new_integrator/device/cuda/cuda_eval_denvars.cu	Removes archived density-variable qualifiers.
attic/src/integrator/cuda/gauxc-cuda_integrator.cmake	Updates legacy CUDA standard.
attic/src/integrator/cuda/cuda_weights.cu	Removes a legacy coordinate qualifier.
attic/src/integrator/cuda/cuda_eval_denvars.cu	Removes legacy density-variable qualifiers.

Review details

• Files reviewed: 11/11 changed files
• Comments generated: 0
• Review effort level: Balanced

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