Algod: Compcert msg into struct

[algonathan]

Summary

Test Plan

[id-ms]

overall looks pretty good.
There are few things I think we should take into consideration

[codecov-commenter]

Codecov Report

Merging #3742 (6c00224) into feature/stateproofs (f9a8d27) will increase coverage by 0.00%.
The diff coverage is 53.17%.

@@                 Coverage Diff                  @@
##           feature/stateproofs    #3742   +/-   ##
====================================================
  Coverage                49.61%   49.61%           
====================================================
  Files                      391      393    +2     
  Lines                    68529    68621   +92     
====================================================
+ Hits                     33998    34047   +49     
- Misses                   30787    30826   +39     
- Partials                  3744     3748    +4     

Impacted Files	Coverage Δ
compactcert/worker.go	90.00% <ø> (ø)
crypto/compactcert/common.go	75.00% <ø> (ø)
daemon/algod/api/server/v1/handlers/handlers.go	0.62% <0.00%> (ø)
data/stateproof/message.go	0.00% <0.00%> (ø)
data/transactions/compactcert.go	23.07% <0.00%> (ø)
ledger/internal/eval.go	66.44% <ø> (ø)
ledger/ledger.go	59.66% <ø> (ø)
data/stateproof/msgp_gen.go	42.18% <42.18%> (ø)
compactcert/signer.go	54.54% <58.33%> (+1.60%)	⬆️
data/transactions/msgp_gen.go	40.39% <58.33%> (ø)
... and 13 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update f9a8d27...6c00224. Read the comment docs.