Extend Nemo AutoTokenizer & SentencePieceTokenizer API for TensorRT-LLM & AMMO evaluation scripts usage
jenkins jenkins LGTM, but can we check if autotokenizer and local sentencepiece outputs match for the new methods implemented before we merge?

it is probably fine if they're not identical, but we need to know where the differences arise and also document them if any This PR is stale because it has been open for 14 days with no activity. Remove stale label or comment or update or this will be closed in 7 days. This PR is stale because it has been open for 14 days with no activity. Remove stale label or comment or update or this will be closed in 7 days. This PR was closed because it has been inactive for 7 days since being marked as stale.
# What does this PR do ?

Extending NeMo's AutoTokenizer and SentencePieceTokenizer for consistency with HuggingFace tokenizers API as it is used throughout TensorRT-LLM and AMMO in evaluation tools.

This is necessary to seamlessly enable model validation -- including quantized variants -- with the current scripts and to avoid code duplication.

Example use-cases to support:
- overall API [link1](https://github.com/NVIDIA/TensorRT-LLM/blob/118b3d7e7bab720d8ea9cd95338da60f7512c93a/tensorrt_llm/hlapi/tokenizer.py#L14-L46)
- `encode`: [link1](https://github.com/NVIDIA/TensorRT-LLM/blob/035b99e0d09d4f2dfdb949810cf7245112aa4165/examples/gpt/run_hf.py#L92) and [link2](https://github.com/NVIDIA/TensorRT-LLM/blob/118b3d7e7bab720d8ea9cd95338da60f7512c93a/examples/summarize.py#L162)
- `decode`: [link1](https://github.com/NVIDIA/TensorRT-LLM/blob/035b99e0d09d4f2dfdb949810cf7245112aa4165/examples/mmlu.py#L295)
- `batch_decode`: [link1](https://github.com/NVIDIA/TensorRT-LLM/blob/118b3d7e7bab720d8ea9cd95338da60f7512c93a/examples/summarize.py#L208)
- `batch_encode_plus` [link2](https://github.com/NVIDIA/TensorRT-LLM/blob/035b99e0d09d4f2dfdb949810cf7245112aa4165/tensorrt_llm/quantization/quantize_by_ammo.py#L204)
- setting  `pad_token_id`: [link1](https://github.com/NVIDIA/TensorRT-LLM/blob/118b3d7e7bab720d8ea9cd95338da60f7512c93a/examples/utils.py#L118-L119)

**Collection**: NLP

# Changelog 

- adding different variants of encode/decode methods
- adding `pad_token_id` (with setter enabled for HF AutoTokenizer wrapper) and `eos_token_id` property attributes for HF tokenizer

# Usage
See examples listed above.

# Jenkins CI
To run Jenkins, a NeMo User with write access must comment `jenkins` on the PR.

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