test: Check for unexpected EOF prefix in tests

[chfast]

In the validate_state() also check for unexpected code with EOF prefix before EOF is enabled. The EIP-3541 prevents such code to be deployed.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (e4bcf7c) 97.79% compared to head (a0ff4f9) 97.95%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #809      +/-   ##
==========================================
+ Coverage   97.79%   97.95%   +0.16%     
==========================================
  Files         110      110              
  Lines       10822    10827       +5     
==========================================
+ Hits        10583    10606      +23     
+ Misses        239      221      -18     

Flag	Coverage Δ
blockchaintests	59.88% <ø> (ø)
statetests	62.16% <0.00%> (?)
statetests-silkpre	25.53% <0.00%> (-0.02%)	⬇️
unittests	95.96% <100.00%> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
test/statetest/statetest_loader.cpp	96.49% <100.00%> (+0.01%)	⬆️
test/unittests/statetest_loader_test.cpp	100.00% <100.00%> (ø)

... and 5 files with indirect coverage changes