TODO:
- Support for `zeta := true` at `apply_beta`.
- Investigate test failure.
- Break PR in pieces because of bootstrapping issues. The current PR
updates a stage0 file to workaround the issue.
Motivation: significant performance improvement at
https://github.com/leanprover/LNSym/blob/proof_size_expt/Proofs/SHA512/Experiments/Sym30.lean
With M1 Pro:
- Before: 4.56 secs
- After: 3.16 secs
Successfully built stage2 using this PR
