Validate proof with ECVRF_decode_proof in vrfEd25519r2ishiguro.ProofToHash()

[Mdaiki0730]

Description

The external function ECVRF_proof2hash() only takes the slice from position 1 to 32 as the hash, but does not check the input vrf proof is valid or not. This implementation violates the ongoing standardization described in section 5.2 of the VRF documentation.
I think it's better to verify the vrf proof before calling r2ishiguro.ECVRF_proof2hash(proof) to keep up with the ongoing standardization.

PR Check List

• Is the current test pattern sufficient?
• Is the ProofToHash error pattern sufficient?

[codecov]

Codecov Report

Merging #493 (d1f3bbf) into main (bf07442) will increase coverage by 0.05%.
The diff coverage is 100.00%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #493      +/-   ##
==========================================
+ Coverage   65.42%   65.47%   +0.05%     
==========================================
  Files         278      278              
  Lines       37923    37928       +5     
==========================================
+ Hits        24811    24835      +24     
+ Misses      11300    11283      -17     
+ Partials     1812     1810       -2     

Impacted Files	Coverage Δ
crypto/vrf/vrf_r2ishiguro.go	100.00% <100.00%> (ø)
blockchain/v0/pool.go	77.77% <0.00%> (-1.30%)	⬇️
consensus/state.go	73.38% <0.00%> (-0.06%)	⬇️
light/client.go	61.61% <0.00%> (ø)
statesync/snapshots.go	93.71% <0.00%> (ø)
p2p/pex/addrbook.go	71.66% <0.00%> (+0.50%)	⬆️
consensus/reactor.go	75.63% <0.00%> (+0.61%)	⬆️
abci/client/socket_client.go	72.96% <0.00%> (+0.87%)	⬆️
mempool/reactor.go	79.67% <0.00%> (+1.09%)	⬆️
privval/signer_listener_endpoint.go	91.26% <0.00%> (+2.38%)	⬆️
... and 2 more

[torao]

LGTM