Fix payload_len calculation for DataPacket.

[Splinter1984]

This PR fix pl_len calculation issue for DataPacket of RTPS protocol.
Take into account the size of inlineQoS during payload length calculation.
Closes #4594

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 80.87%. Comparing base (ef72e1d) to head (1bb70c5).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4545      +/-   ##
==========================================
+ Coverage   80.48%   80.87%   +0.38%     
==========================================
  Files         368      368              
  Lines       90255    90256       +1     
==========================================
+ Hits        72645    72992     +347     
+ Misses      17610    17264     -346     

Files with missing lines	Coverage Δ
scapy/contrib/rtps/common_types.py	95.31% <100.00%> (+0.03%)	⬆️
scapy/contrib/rtps/rtps.py	100.00% <100.00%> (+1.17%)	⬆️

... and 23 files with indirect coverage changes

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