crypto: add SHA-512 hashes

[cce]

Summary

This adds SHA-512 hashing to the block header, including the transaction commitment. When #3829 was added, a generic hashing abstraction and a new vector commitment implementation were added that supports both 64-byte (sumhash) and 32-byte (SHA-256, SHA-512/256) hashes, so not many changes were needed.

Matching go-algorand-sdk PR in algorand/go-algorand-sdk#723

Test Plan

Existing tests should pass; in addition, #3829 added some tests for SHA-256 transaction commitments that could be copy/pasted into this PR for SHA-512.

[codecov]

Codecov Report

Attention: Patch coverage is 59.37500% with 13 lines in your changes missing coverage. Please review.

Project coverage is 51.89%. Comparing base (6f65ab1) to head (2c061fa).
Report is 29 commits behind head on master.

Files with missing lines	Patch %	Lines
crypto/hashes.go	0.00%	6 Missing ⚠️
data/bookkeeping/block.go	72.72%	3 Missing and 3 partials ⚠️
data/bookkeeping/genesis.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #6339      +/-   ##
==========================================
- Coverage   51.90%   51.89%   -0.02%     
==========================================
  Files         653      653              
  Lines       87469    87500      +31     
==========================================
+ Hits        45399    45405       +6     
- Misses      39197    39219      +22     
- Partials     2873     2876       +3     

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[Copilot]

Pull Request Overview

Adds support for SHA-512 hashing in block headers and transaction commitments.

• Introduces a new Branch512 field on BlockHeader and wires it through PreCheck, serialization, and genesis/block creation.
• Adds TxnMerkleTreeSHA512 and paysetCommitSHA512 alongside the existing SHA-256 and SHA-512/256 commitments.
• Updates consensus parameters, tests, and regenerated MsgPack code to account for the new 64-byte fields.

Reviewed Changes

Copilot reviewed 14 out of 14 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
protocol/tags.go	Increased ProposalPayloadTagMaxSize for extra hash.
data/bookkeeping/genesis.go	Modified genesis block initialization of TxnCommitments.
data/bookkeeping/txn_merkle.go	Added TxnMerkleTreeSHA512 method.
data/bookkeeping/block.go	Added Branch512, Hash512, paysetCommitSHA512; integrated into MakeBlock and PreCheck.
data/bookkeeping/msgp_gen.go	Regenerated MsgPack code to include new fields.
crypto/hashes.go	Added Sha512 type, Sha512Digest, and hash factory case.
config/consensus.go	Introduced EnableSha512BlockHash flag and enabled it for future protocols.
crypto/msgp_gen.go & crypto/msgp_gen_test.go	Added MsgPack support and tests for Sha512Digest.
catchup/catchpointService_test.go	Updated test to set Branch512 on downloaded blocks.
(plus extensive autogenerated changes in agreement/msgp_gen.go and transmittedPayload code)