fix(testing): remove ignored StateTest engine_api_error_code

[junbyjun1238]

🗒️ Description

Remove engine_api_error_code from StateTest.

StateTest currently exposes engine_api_error_code, but the value is silently dropped during the StateTest -> Block conversion in state.py. The native state-fixture path does not consume it either, so the current API advertises a field that is effectively ignored.

This field no longer matches the current codebase's abstraction:

• engine_api_error_code is modeled as block/payload metadata in blockchain.py and fixtures/blockchain.py
• all current in-repo usages attach it to Block(...), not StateTest(...)
• unlike block_exception, it is not wired through _generate_blockchain_blocks() and has no in-tree StateTest(...) call sites

Removing the field makes the API honest and avoids a footgun where a test author can specify an Engine API error expectation that is silently ignored. With BaseTest configured as extra="forbid", unsupported usage will fail fast at model construction rather than being silently ignored.

🔗 Related Issues or PRs

N/A.

✅ Checklist

• All: Ran fast static checks to avoid unnecessary CI fails:

  just static

• All: PR title adheres to the repo standard and starts with type(scope):.
• All: Considered updating the online docs in ./docs/.
• All: Set appropriate labels for the changes (only maintainers can apply labels).

Cute Animal Picture

[felix314159]

yes StateTest.engine_api_error_code is currently ineffective, but removing it changes the public API and may break downstream clients relying on it. i would prefer to just keep it as is for compatibility and close this PR, unless you can explain your motives for this change?

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 86.47%. Comparing base (40461a6) to head (b17b695).
⚠️ Report is 14 commits behind head on forks/amsterdam.

Additional details and impacted files

@@                 Coverage Diff                 @@
##           forks/amsterdam    #2740      +/-   ##
===================================================
+ Coverage            86.26%   86.47%   +0.21%     
===================================================
  Files                  599      599              
  Lines                37038    37632     +594     
  Branches              3795     3795              
===================================================
+ Hits                 31949    32542     +593     
- Misses                4525     4526       +1     
  Partials               564      564              

Flag	Coverage Δ
unittests	86.47% <ø> (+0.21%)	⬆️

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[felix314159]

interesting, CI passed. maybe it is fine to go ahead with this after all

[junbyjun1238]

I've reviewed it again, and I now think the upside is mostly API cleanup while the downside is downstream compatibility risk — so I lean toward not making the change. The benefit seems smaller than the risk.
This PR wasn't driven by anything specific either. I noticed it while studying the codebase and opened a cleanup PR around it. I'll review the tradeoffs more carefully before opening similar PRs in the future.