rand

Merge pull request #1202 from adamreichold/numpy-compat

Extend generator benchmarks to include the newly added Pcg64Dxsm variant.

Apply the same copy-editing to the existing generators as was discussed for Lcg128CmDxsm64.

Add Lcg128CmDxsm64 generator compatible with NumPy's PCG64DXSM.

Replace the open-coded fill_bytes_impl by rand_core::impls::fill_bytes_via_next.