crypto: add go-based BatchVerifier implementation

[cce]

Summary

This adds a pure-Go ed25519 BatchVerifier implementation using on the ed25519consensus library, plus additional checks to preserve our ed25519 validation criteria, last updated in #3031 (reject small order A; reject non-canonical A, R, S; use the cofactor equation).

Like our libsodium batch verification implementation, the IsCanonicalY check here is also based on the "Taming the Many EdDSAs" paper in https://eprint.iacr.org/2020/1244

Test Plan

New tests added to compare ed25519 criteria results match our existing libsodium- and ed25519-donna-based batch verification implementation (from #3031 and defined in algorandfoundation/specs#60). New test helpers run test vectors with different batch sizes, taken from

• 12 edge cases from "Taming the many EdDSAs" Appendix C, Table 6c, also used in our libsodium fork's tests in batch verification: add ed25519 batch verification implementation #3031
• 1025 successful cases from our libsodium fork's tests, also added in batch verification: add ed25519 batch verification implementation #3031.
• 196 edge cases used to draw the 14x14 grid visualizations from the blog post "It's 255:19AM. Do you know what your validation criteria are?" and used in ed25519consensus
• 768 edge cases from the Go crypto package's crypto/ed25519/ed25519vectors_test.go

[codecov]

Codecov Report

❌ Patch coverage is 82.70677% with 23 lines in your changes missing coverage. Please review.
✅ Project coverage is 50.72%. Comparing base (8245ed1) to head (b809fa7).
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
crypto/gobatchverifier.go	91.08%	6 Missing and 3 partials ⚠️
crypto/batchverifier.go	72.00%	7 Missing ⚠️
crypto/onetimesig.go	0.00%	7 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #6440      +/-   ##
==========================================
- Coverage   50.84%   50.72%   -0.12%     
==========================================
  Files         664      658       -6     
  Lines      111455   111478      +23     
==========================================
- Hits        56665    56552     -113     
- Misses      51924    52044     +120     
- Partials     2866     2882      +16     

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[cce]

OK, updated with @jannotti's feedback and brought in more test vectors from crypto/ed25519/ed25519vectors_test.go plus new tests specifically for isCanonicalPoint and hasSmallOrder.