bug(test-cli-fill): Use default evm-dump-dir for traces; gitignore it

[fselmo]

🗒️ Description

• --traces with --evm-dump-dir is currently broken due to improper LazyAlloc handling. This PR fixes it by validating with get() and properly serializing via model_dump_json.
• Use a default --evm-dump-dir of traces/ which is also in .gitignore so we don't have to keep removing it from the working dir. Previously, --traces did absolutely nothing without a specified --evm-dump-dir but it also didn't tell you anything in the cli if you did this, which is quite confusing DevEx.

🔗 Related Issues or PRs

✅ 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: Considered adding an entry to CHANGELOG.md.
• All: Considered updating the online docs in the ./docs/ directory.
• All: Set appropriate labels for the changes (only maintainers can apply labels).

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 83.87%. Comparing base (2a6f9ee) to head (5f21c42).
⚠️ Report is 15 commits behind head on forks/osaka.

Additional details and impacted files

@@               Coverage Diff               @@
##           forks/osaka    #1852      +/-   ##
===============================================
- Coverage        87.31%   83.87%   -3.45%     
===============================================
  Files              541      402     -139     
  Lines            32832    25101    -7731     
  Branches          3015     2285     -730     
===============================================
- Hits             28668    21053    -7615     
- Misses            3557     3609      +52     
+ Partials           607      439     -168     

Flag	Coverage Δ
unittests	83.87% <ø> (-3.45%)	⬇️

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[marioevz]

Just one change I think should be a good optimization to make.

[marioevz]

LGTM, thanks!