Incorporate safetensors support to TorchAO (#13719)
* Incorporate safetensors support to TorchAO
* Address TorchAO safetensors review comments
* Address TorchAO safetensors review feedback
* Address follow-up TorchAO review feedback
* Simplify TorchAO metadata loading guard
* Address TorchAO test utility review feedback
* Scope TorchAO safetensors to quantizer hooks
* Use tensor assertion helper in TorchAO tests
* ruff
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Co-authored-by: Dhruv Nair <dhruv.nair@gmail.com>
Co-authored-by: Sayak Paul <spsayakpaul@gmail.com>
