TRT-LLM export P-tuning related fixes
# What does this PR do ?

Fixes the implementation of PEFT for TRT-LLM export.

**Collection**: NLP

# Changelog 

- Add the bos token to LLAMA based models (not just P-tuning related, improves LLAMA results in general).
- Remember the vtoken counts for each p-tuning table when the tables are added.
- Prepend the right number of vtokens to each query based on its task_id.
- Preserve the dtype of the p-tuning table when it is padded.
- Validate that all p-tuning tables fit into max_prompt_embedding_table_size limit.

 
**PR Type**:
- [ ] New Feature
- [X] Bugfix
- [ ] Documentation

# Additional Information
* Related to bug 4350064
