Add TCPCLv4 message definitions and tcp_reassemble interface

[BrianSipos]

Description

This is a port of earlier TCPCL packet definitions from dtn-demo-agent with more modern scapy-friendly patterns of dispatchers and with a tcp_reassemble() interface.

This is an alternative to part of #4824 with some simplified structures.
Test capture files are included for demonstration.

[codecov]

Codecov Report

❌ Patch coverage is 94.47853% with 9 lines in your changes missing coverage. Please review.
✅ Project coverage is 79.81%. Comparing base (6aea6cf) to head (517c267).
⚠️ Report is 42 commits behind head on master.

Files with missing lines	Patch %	Lines
scapy/contrib/tcpcl.py	94.47%	9 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5076      +/-   ##
==========================================
- Coverage   80.50%   79.81%   -0.70%     
==========================================
  Files         390      373      -17     
  Lines       96785    96622     -163     
==========================================
- Hits        77919    77120     -799     
- Misses      18866    19502     +636     

Files with missing lines	Coverage Δ
scapy/contrib/tcpcl.py	94.47% <94.47%> (ø)

... and 302 files with indirect coverage changes

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