Fixes for ROCM on AMD and HIP on NVIDIA codepaths
- Bugfixes for missing AMD kernels in merge_systems (solve_tridi)
- Fix AMD runtime error: bug in gpu_update_ndef_c (merge_systems)
- Fix usage of rocsolver/hipsolver for new gpusolver_syevd function.
- Treat hipsolver handles in a way symmetric to cusolver handles