cuRAND replacement

[LWisteria]

Current random generator is too simple and poor.

We need to replace cuRAND.

[yuk-to]

cupyとcuRANDをざっと見る限り、XORSHIFTを実装すれば良さそう。なお、cupy側としてはcuRANDのどのアルゴも呼べるようにしてある。

ref:

• https://github.com/cupy/cupy/blob/master/tests/cupy_tests/cuda_tests/test_curand.py
• https://github.com/cupy/cupy/blob/f94c699831b16afad273aa3ecfe302147a8984e6/cupy/random/generator.py#L47
• https://docs.nvidia.com/cuda/curand/group__HOST.html (When rng_type is CURAND_RNG_PSEUDO_DEFAULT, the type chosen is CURAND_RNG_PSEUDO_XORWOW)