Torch 2.6.0 upgrade

[lorenzomammana]

Summary

Upgrade torch from 2.4.1 to 2.6.0

Added

• Add a way to use validation data to evaluate ONNX fp16 mixed precision export

Updated

• Update torch to 2.6.0+cu126 and torchvision to 0.21.0+cu126
• Increase minimum rtol and atol for finetuning model export to avoid errors on efficientnet_b0 export

Type of Change

Please select the one relevant option below:

• Breaking change

Checklist

Please confirm that the following tasks have been completed:

• I have tested my changes locally and they work as expected. (Please describe the tests you performed.)
• I have added unit tests for my changes, or updated existing tests if necessary.
• I have updated the documentation, if applicable.
• I have installed pre-commit and run locally for my code changes.