🧪 Test header raw modifications

[ffalcinelli]

🎯 What: The testing gap addressed
The codebase had untested paths in pydivert/packet/header.py for the setter of raw inside the Header class, as well as raw, payload, src_port, and dst_port inside RawProtocol, PayloadMixin, and PortMixin.

📊 Coverage: What scenarios are now tested
A new test called test_header_raw_modification was added in pydivert/tests/test_packet.py. It tests:

• Replacing the raw bytes of an ipv4 header with bytes of the exact same length.
• Replacing the raw bytes of an ipv4 header with bytes of a different length, and ensuring packet_len updates accordingly.
• A Dummy protocol implementing PortMixin and PayloadMixin was written to test the specific byte manipulation logic isolated from concrete Header overrides.

✨ Result: The improvement in test coverage
pydivert/packet/header.py now receives thorough test coverage on all these previously unverified paths, and their associated # pragma: no cover statements have been safely removed.

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PR created automatically by Jules for task 2581065931698872938 started by @ffalcinelli

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.47%. Comparing base (51364d0) to head (1d22b08).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #146   +/-   ##
=======================================
  Coverage   98.46%   98.47%           
=======================================
  Files          20       20           
  Lines        2350     2356    +6     
  Branches      216      218    +2     
=======================================
+ Hits         2314     2320    +6     
  Partials       36       36           

Files with missing lines	Coverage Δ
pydivert/packet/header.py	97.91% <100.00%> (+0.29%)	⬆️

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