SYCL NBNXM offload support

SYCL NBNXM offload support

Associated changes:

- Added function stubs to PME: necessary for compilation.
- Stricter SYCL hardware compatibility checks: limits on subgroup size
  and the availability of local memory.
- The kernel implementation and overall logic closely follow the OpenCL
  implementation. Divergences are documented locally.

Limitations:

- No fine-grained timings yet.
- Code-duplication with CUDA and OpenCL: see #2608.
- Minor differences in local/nonlocal synchronization: see #3895,
  related to #2608.
- Only the OpenCL backend was extensively tested. LevelZero works fine
  without MPI but stalls due to a known bug. The fix for DPCPP runtime
  is available, but not yet part of any OneAPI release:
  https://github.com/intel/llvm/pull/3045.
- The complex/position-restraints regression test fails: see #3846.
- No performance tuning: see #3847.

Performance on rnase-cubic system is similar to OpenCL implementation.