When running the submission_runner on the self-tuning track, we run into this error calling `_signed_to_unsigned` from random_utils.py. 

I've added a fix

```ValueError: Seed must be between 0 and 2**32 - 1
    rng = prng.PRNGKey(rng_seed)
  File "/private/home/axyang/optimization/algorithmic-efficiency-entry/algorithm
ic_efficiency/random_utils.py", line 79, in PRNGKey
    return _PRNGKey(seed)
```

[fix] random_utils.py to `_signed_to_unsigned`

Fix path in helper config for running experiments in bulk.

Finalize variants targets

Aiming to Fix Conformer OOM

Lint fixes

Add warning for PyTorch data loader num_workers flag.