statetest: Drop support for "fake" `BLOCKHASH`

[chfast]

The state tests had a procedure of generating non-empty BLOCKHASH outputs based on the block number. This is deprecated feature not used in any existing tests. Remove support for it in evmone.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 94.22%. Comparing base (8399303) to head (b778311). Report is 11 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    ethereum/execution-spec-tests#1049      +/-   ##
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- Coverage   94.23%   94.22%   -0.01%     
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  Files         155      155              
  Lines       15968    15959       -9     
==========================================
- Hits        15047    15038       -9     
  Misses        921      921              

Flag	Coverage Δ
eof_execution_spec_tests	17.70% <0.00%> (+0.01%)	:arrow_up:
ethereum_tests	27.50% <100.00%> (+<0.01%)	:arrow_up:
ethereum_tests_silkpre	19.36% <0.00%> (+<0.01%)	:arrow_up:
execution_spec_tests	20.62% <0.00%> (+0.01%)	:arrow_up:
unittests	89.01% <0.00%> (-0.02%)	:arrow_down:

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Files with missing lines	Coverage Δ
test/state/host.cpp	100.00% <100.00%> (ø)
test/unittests/state_transition_block_test.cpp	100.00% <ø> (ø)

[winsvega]

Perhaps error out of invalid test?

[chfast]

Perhaps error out of invalid test?

How exactly?

[chfast]

We may get a protection against this in EEST: https://github.com/ethereum/execution-specs/issues/1500.

But it may also break goevmlab fuzzer (cc @holiman). However, they may use "blockHashes" to provide the value for BLOCKHASH(0).

[holiman]

What do you mean "deprecated feature" - since the opcode BLOCKHASH is still not deprecated, what is a node supposed to do on that opcode, when executing a statetest?

[chfast]

What do you mean "deprecated feature" - since the opcode BLOCKHASH is still not deprecated, what is a node supposed to do on that opcode, when executing a statetest?

State tests try to avoid it at all cost to the point a state test with BLOCKHASH is considered invalid. See https://github.com/ethereum/execution-specs/issues/1500.

[holiman]

I think that is insufficient. Random tests are highly useful. I don't much care what the vm returns, but having all vms behave identically is important.

Why do this?

[chfast]

Why do this?

It bothers me this is mixed with the semi-production ready code. I'd prefer returning null hash but I think we can find a place for the old behavior...

[chfast]

The ethereum/execution-spec-tests#1059 moves this feature "more" into "tests only". This should be fine for now.