Make _StorageBase.byteswap faster ( > 10000x) (#101925)
This PR addresses #101690. This PR implement faster data elements swap in `_StorageBase` using C++ rather than using Python.
This PR helps such a situation that a large model saved on a little-endian machine will be loaded on a big-endian machine.
TODO:
- [x] Add test cases
- [x] Add performance comparison before and after the PR
- [ ] (Optional) Investigate further opportunities for performance improvements by [SIMDization](https://dev.to/wunk/fast-array-reversal-with-simd-j3p)
Fixes #101690
Pull Request resolved: https://github.com/pytorch/pytorch/pull/101925
Approved by: https://github.com/mikaylagawarecki
