migration vrf library from r2ishiguro to curve25519-voi

[zemyblue]

Summary

We replace the Ostracon's vrf library from r2ishiguro to curve25519-voi by #620 and #633. But this change has a consensus breaking change, So this Ostracon need to add the migration logic from r2ishiguro to curve25519-voi

Problem Definition

The r2ishiguro vrf library was removed by #633. We still need it to verify a previous blocks.

Proposal

• Need to add r2ishiguro vrf library again.
• Need to add a migration algorithm (r2ishiguro -> curve25519-voi)
• Need to add the feature to prevent to reuse r2ishiguro after migrating to curve25519-voi.

---

For Admin Use

• [ ] Not duplicate issue
• [ ] Appropriate labels applied
• [ ] Appropriate contributors tagged
• [ ] Contributor assigned/self-assigned

[0Tech]

652 addresses the issue. Here is a brief description:

• Need to add r2ishiguro vrf library again.
  • Import the legacy logic into crypto/ed25519/internal/r2ishiguro, which hides the implementation from the other packages.
• Need to add a migration algorithm (r2ishiguro -> curve25519-voi)
  • Allow the new ostracon to verify the old r2ishiguro proofs.
  • Generation of the proof (by VRFProve()) always done by the new implementation, curve25519-voi.
• Need to add the feature to prevent to reuse r2ishiguro after migrating to curve25519-voi.
  • Introduce "versioned vrf" global instance, which manages its own version.
  • The version would be updated if it encounters a proof by a new implementation.
  • Implementation with old version CANNOT be used.