trunk/903d704d38916437fd995fdbc0db031e72de92d9: [Stable-ABI] Add torch::stable::from_file. (#198263)

Executive Summary

Adds torch::stable::from_file to the stable ABI. Needed for torchvision stable-ABI, which currently carries a local stable_from_file helper for image decoding. Summary Introduces torch::stable::from_file and it returns a 1-D tensor backed by a memory-map of the file. Functional differences between the ATen and stable signatures include filename being const std::string& rather than std::string_view .

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