Add support for QuadS separable quadrature splines in SOGKSpace

- Introduced a new boolean flag `is_quads` in `SOGKSpace` to select between CubeS₂ and QuadS methods.
- Added a new vector `mesh_green_self_virial` to store self-energy strain-derivative virial data.
- Updated GPU state structure to include `d_gsv` for bare K_v(k²) self-energy strain-derivative virial.
- Modified kernel functions to compute self-energy contributions and updated reduction logic to handle additional virial terms.
- Enhanced spline weight calculations for QuadS order 4 and 6, ensuring correct coefficients and offsets.
- Updated GPU setup and compute functions to accommodate new parameters and memory allocations.
- Adjusted memory management to free new GPU resources and ensure compatibility with existing structures.

Author: Johnsonjz