refactor(test-types): add common BytesConcatenation to execution_testing

[chfast]

🗒️ Description

This brings the copy-paste BytesConcatenation from tests/ to ethereum_testing.base_types.

🔗 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: 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).

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 87.31%. Comparing base (9523e75) to head (0cbb3f3).
⚠️ Report is 11 commits behind head on forks/osaka.

Additional details and impacted files

@@             Coverage Diff              @@
##           forks/osaka    #1858   +/-   ##
============================================
  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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[spencer-tb]

Very welcome change from my side. LGTM

[marioevz]

LGTM, thanks!