Whisper model support in Lite
I made some changes to enable the training to converge (commit https://github.com/NVIDIA/NeMo/pull/11464/commits/c605d12aa89f8674e6a11141a0e7fdd4c9e80c5c):
* Preserve HF tokenizer's Whisper special tokens (prompt)
* Change the precision to bf16 (fp16 results in nan after the first weight update)
* Fix decoder_input_ids and labels for training step [🤖]: Hi @oyilmaz-nvidia 👋,

We wanted to let you know that a [CICD pipeline](https://github.com/NVIDIA/NeMo/actions/runs/12476579837) for this PR just finished successfully

So it might be time to merge this PR or get some approvals

I'm just a bot so I'll leave it you what to do next.

//cc @pablo-garay @ko3n1g
# What does this PR do ?

Adds AutoModelSeq2Seq HF support
