Add ROCm backward compatibility test for cholesky solver
- Add test data file rocm_cholesky_solver_potrf.py with data for f32, f64, and c64 dtypes
- Update test_gpu_cholesky_solver_potrf to support both CUDA and ROCm platforms
- Add rocm_cholesky_solver_potrf.data_2026_02_05 to covering_testdatas
- Remove hipsolver_potrf_ffi from manually ignored targets (now covered by test)
