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 87.31%. Comparing base (2a6f9ee) to head (0793283).
⚠️ Report is 1 commits behind head on forks/osaka.

Additional details and impacted files

@@             Coverage Diff              @@
##           forks/osaka    #1852   +/-   ##
============================================
  Coverage        87.31%   87.31%           
============================================
  Files              541      541           
  Lines            32832    32832           
  Branches          3015     3015           
============================================
  Hits             28668    28668           
  Misses            3557     3557           
  Partials           607      607           

Flag	Coverage Δ
unittests	87.31% <ø> (ø)

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