Update to vLLM 0.5.3.post1, LLAMA3.1 support
Please update the base branch to `main`. > Please update the base branch to `main`.

Done.
# What does this PR do ?

Updates the vLLM integration to work with the latest version at this time, fixes the HF->NeMo conversion script to handle the LLAMA3.1-8B checkpoint.

**Collection**: NLP
