Allow pre-commit hook to sync c10 headers between ET and pytorch

[larryliu0820]

This pull request enhances the workflow for updating the PyTorch commit pin by also automatically syncing the c10 directories between ExecuTorch and PyTorch. The changes update both the pre-commit hook and the update script to ensure that any time the PyTorch pin is updated, the corresponding source files in runtime/core/portable_type/c10/ are checked and grafted from PyTorch if needed. This helps keep the local codebase consistent with upstream changes and reduces manual maintenance.

Pre-commit hook improvements:

• The .githooks/pre-commit script now triggers both the PyTorch pin update and the c10 directory sync whenever torch_pin.py is changed, and automatically stages any modified files for commit.

Sync logic and automation:

• Added new functions in .github/scripts/update_pytorch_pin.py to compare files in ExecuTorch's c10 and torch/headeronly directories against the corresponding PyTorch repo files at the pinned commit, and graft upstream changes when differences are detected.
• The script fetches file content directly from GitHub using the API, skipping build files and handling missing files gracefully.
• The main update script now calls the new sync logic after updating the commit pin, and provides clear output indicating the number of files grafted or confirming directories are in sync.

Dependency and import updates:

• Added necessary imports (base64, hashlib, Path) to support file comparison and GitHub API interactions in the update script.

[pytorch-bot]

🔗 Helpful Links

🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/executorch/15184

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[github-actions]

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[Gasoonjia]

LGTM! And i believe you've tested locally right