Don't use batched ed25519 signatures verification

[tomaka]

I didn't realize that they were broken.

[tac0turtle]

Not sure how its broken, but a suggestion would be to adopt zip215: https://hdevalence.ca/blog/2020-10-04-its-25519am. https://github.com/ZcashFoundation/ed25519-zebra already implements it and is safe to use in consensus critical areas.

[burdges]

Yup dalek-cryptography/ed25519-dalek#117 It becomes safe if one always uses stricter verification, and less nasty if one only ever uses one unique deterministic batch. In the second case, a node could create a block with all valid signatures that passes validation, but technically contains some invalid signatures.