feat(tools): use Hardfork for fork module loading

[JackCC703]

🗒️ Description

Adds Hardfork.by_short_name() and uses Hardfork.module() in tooling paths that previously loaded fork modules through hardcoded ethereum.forks.<fork> paths.

This centralizes short-name fork lookup and removes duplicated fork discovery logic from optimized patches, fixture loading, JSON VM loading, and t8n fork-specific helpers.

🔗 Related Issues or PRs

Fixes #1426.

✅ Checklist

• All: Ran fast static checks to avoid unnecessary CI fails, see also Code Standards and Enabling Pre-commit Checks:

  just static

• All: PR title adheres to the repo standard - it will be used as the squash commit message and should start type(scope):.
• All: Considered updating the online docs in the ./docs/ directory.
• All: Set appropriate labels for the changes (only maintainers can apply labels).
• Tests: Ran mkdocs serve locally and verified the auto-generated docs for new tests in the Test Case Reference are correctly formatted.
• Tests: For PRs implementing a missed test case, update the post-mortem document to add an entry the list.
• Ported Tests: All converted JSON/YML tests from ethereum/tests or tests/static have been assigned @ported_from marker.

Cute Animal Picture

[SamWilsn]

Looks fine to me. Just the one potential improvement.

[SamWilsn]

Is there anywhere that uses fork_name: str left? Would be nice to just avoid the Union here.

[JackCC703]

Thanks, fixed in ee910c4. The optimized helpers now take Hardfork directly, and the internal str compatibility path is gone. I checked the callers and they already pass Hardfork instances.

I also moved the helper test so it does not get collected by the filler/docs jobs.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 88.62%. Comparing base (6333758) to head (ee910c4).
⚠️ Report is 5 commits behind head on forks/amsterdam.

Additional details and impacted files

@@                 Coverage Diff                 @@
##           forks/amsterdam    #2778      +/-   ##
===================================================
+ Coverage            88.17%   88.62%   +0.45%     
===================================================
  Files                  577      577              
  Lines                35659    35659              
  Branches              3490     3490              
===================================================
+ Hits                 31442    31604     +162     
+ Misses                3654     3492     -162     
  Partials               563      563              

Flag	Coverage Δ
unittests	88.62% <ø> (+0.45%)	⬆️

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