Model config_format and tokenizer_mode conditional defaults fix

[Daniel-Schenker]

Description

This PR updates the logic used to apply conditional defaults for config_format and tokenizer_mode.

The previous implementation was incorrectly assigning mistral formatting to Llama models from HF as it was recursively searching the model files for a params.json file which was present in a subdirectory of some Llama models.

The new implementation uses is_mistral_model_repo which checks for consolidated*.safetensors file which is a more accurate check for mistral models.

Related Issues

Test Plan

Tested with various supported models and it correctly detects mistral for supported mistral family models while defaulting to auto for non-mistral models.

Checklist

• I have read the contributing guidelines
• My code follows the project's code style (run bash format.sh)
• I have added tests for my changes (if applicable)
• I have updated the documentation (if applicable)
• My commits include a Signed-off-by: line (DCO compliance)

[github-actions]

👋 Hi! Thank you for contributing.
Just a reminder: Make sure that your code passes all the linting checks, otherwise your PR won't be able to be merged. To do so, run ./format.sh.
Now you are good to go 🚀.

We also recommend installing prek and configuring it to check your code before every local commit.

[joerunde]

lpgtm