Implement _VariableFunctionsClass.randint of torch

[athitten]

🚀 Feature

Implement _VariableFunctionsClass.randint

Motivation

NeMo Stable Diffusion

cc @tfogal

[tfogal]

triage team: what guarantees do we need to provide w.r.t. the generated random numbers? i.e. do we need to match torch exactly, match the same distribution, merely respect the low/high parameters?

NeMo does occasionally use the dtype parameter, and sometimes it's even float32 or similar instead of some integer. We might want to map this an RNG op + a cast.

[mruberry]

triage review — we currently don't require matching anything; we would accept an implementation of randint that calls PyTorch's randint