Add HuggingFace arg so that arch is automatic

[Quentin-Anthony]

Stas Bekman had the idea of supporting a HuggingFace model as input so that all model architecture settings don't need manually dug up. We'd like something like:

python transformer_mem.py --hf_model_name_or_path meta-llama/Llama-2-7b-hf --num-gpus 8 --zero-stage 3 --batch-size-per-gpu 2 --sequence-length 4096

[bhavnicksm]

Hey @Quentin-Anthony,
is someone working on this? If not, I can try to make a PR for this.

[Quentin-Anthony]

Nobody is. I'd love a PR!

[bhavnicksm]

@Quentin-Anthony, created a draft PR, we can continue the conversation there