fix(tests): EIP-7883 minor fixes

[pdobacz]

🗒️ Description

Two unrelated fixes to the EIP-7883 testing:

• fixing the gas formula - I'm not sure why the (len(modexp_expected) // 32) factor was there, as the number of SSTOREs never depended on the length. At the same time there were several SSTOREs done throughout the test. Also the precompile gas part of the tx gas must take into account that the 63/64th rule is going to apply
• new gas should apply for forks coming after Osaka, so that forks that might not define its relation to Osaka use old gas

🔗 Related Issues or PRs

N/A.

✅ Checklist

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

  uvx tox -e static

• All: PR title adheres to the repo standard - it will be used as the squash commit message and should start type(scope):.
• All: Set appropriate labels for the changes (only maintainers can apply labels).

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 86.07%. Comparing base (720caf4) to head (7287589).
⚠️ Report is 2 commits behind head on forks/amsterdam.

Additional details and impacted files

@@               Coverage Diff                @@
##           forks/amsterdam    #2082   +/-   ##
================================================
  Coverage            86.07%   86.07%           
================================================
  Files                  599      599           
  Lines                39472    39472           
  Branches              3780     3780           
================================================
  Hits                 33977    33977           
  Misses                4862     4862           
  Partials               633      633           

Flag	Coverage Δ
unittests	86.07% <ø> (ø)

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[fselmo]

This lgtm, really nice find 👍🏼. Just one clarifying question for a bit more accuracy here before approving.

[fselmo]

Thanks!