Ensure removal of temp files on error in ONNX INT4 quantization (#1359)

### What does this PR do?

Type of change: Minor bug fix


- Put quantization steps inside try-finally to ensure removal of temp
files on error in ONNX INT4 quantization.
- To avoid redundancy between awq_lite() and awq_clip() methods, created
a utility _remove_augmented_onnx() for exception-handling based removal
of augmented onnx file and its data file.

### Testing

- Locally performed ONNX INT4 awq-lite and awq-clip quantization with
Llama 1B model.

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### Additional Information
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<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

* **Refactor**
* Improved reliability of the quantization pipeline by ensuring
temporary conversion artifacts are always removed, making cleanup more
robust.
* Consolidated handling of external-data companions and added safer
deletion behavior that logs failures instead of raising errors.
* Ensured consistent session teardown and forced memory collection to
reduce resource leakage and intermittent errors during model conversion.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

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Signed-off-by: vipandya <vipandya@nvidia.com>

Author: vishalpandya1990