Fix state hash size check in fast implementation

[mininny]

Description

The fast implementation calculates the state hash from the state witness in the StateWitness.StateHash function.

However, this function implements a length check that is insufficient. The expected length is known to be 362 but the implementation checks that the length is greater than 32 + 32 + 8 + 8 + 1 = 81. We should check the state witness length is equal to the expected length.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 50.00000% with 2 lines in your changes missing coverage. Please review.

Project coverage is 61.86%. Comparing base (bf4e465) to head (f0395da).

Files with missing lines	Patch %	Lines
rvgo/fast/state.go	50.00%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #118      +/-   ##
==========================================
- Coverage   61.87%   61.86%   -0.01%     
==========================================
  Files          27       27              
  Lines        4126     4125       -1     
==========================================
- Hits         2553     2552       -1     
  Misses       1432     1432              
  Partials      141      141              

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