read system token from data in gpt_sft_chat_dataset
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. @yidong72 Shall we contact someone to conduct the CI?  > @yidong72 Shall we contact someone to conduct the CI?

I think we need to add "RUN CICD" label to it. let's see if it kicks off the tests 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. @yidong72  can you review it again? I updated the `get_prompt_template_example` function. 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. > @yidong72 can you review it again? I updated the `get_prompt_template_example` function.

gentle ping @yidong72  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. @yidong72 @ko3n1g Please take a look at it. Thanks! 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 ?

The original implementation of the prompt template in `gpt_sft_chat_dataset.py` uses a fix system token `System`. 

This PR enables to read the system token from the dataset so that it is configurable. This enables us to include more prompt templates such as the llama3 prompt template.

**Collection**: [Note which collection this PR will affect]

# Changelog 
- Add specific line by line info of high level changes in this PR.

# Usage
* You can potentially add a usage example below

```python
# Add a code snippet demonstrating how to use this 
```

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