Revert Build Versions from Content Hash to Commit Hash (#29663)

https://github.com/facebook/react/pull/29236 caused issues for internal
syncs at Meta, because we were computing version numbers using file
hashes (to eliminate "no-op" internal sync commits). The problem is that
since version numbers may not be consistent across synced files (e.g. if
some files have not changed in recent commits), the newly introduced
version mismatch check fails.

There's some more work that needs to be done here to restore the
benefits of file-specific hashing, but for now this simply reverts the
content hash changes from the following PRs:

- https://github.com/facebook/react/pull/28633
(95319ab5afd384f5858f7c080573b9736e6b2f9c)
- https://github.com/facebook/react/pull/28590
(37676aba76a9b97e1059e6dec39c3f401f44248d)
- https://github.com/facebook/react/pull/28582
(cb076b593cec3a92338958f58468cce19cb8f0d9)
- https://github.com/facebook/react/pull/26734
(5dd90c562354758942c833b0a46923176e92208e)
- https://github.com/facebook/react/pull/26331
(3cad3a54eda7b2d1c670c2d414f33d78a4c3f6af)