🧪 Add unit tests for IPv4 fragmentation flags

[ffalcinelli]

🎯 What: Added tests for IP packet fragmentation flags. The gap addressed was that test_ipv4_fields didn't thoroughly test properties like rf, reserved, df and mf to make sure they're accurately changed independently.

📊 Coverage: The tests cover the initial state of the flags, testing them individually and independently, as well as a combined combination, preventing regressions.

✨ Result: Improved test coverage for packet fragmentation functionality.

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PR created automatically by Jules for task 8133250723207432189 started by @ffalcinelli

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.46%. Comparing base (9b201a2) to head (bf228e5).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #144   +/-   ##
=======================================
  Coverage   98.46%   98.46%           
=======================================
  Files          20       20           
  Lines        2350     2350           
  Branches      216      216           
=======================================
  Hits         2314     2314           
  Partials       36       36           

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