Reformat Packet++ documentation to use triple-slash doxygen format.

[Dimi1010]

Part of #1658
Includes reformatting of classes, structs and namespace documentation.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 83.16%. Comparing base (f81ced2) to head (217a620).

Additional details and impacted files

@@            Coverage Diff             @@
##              dev    #1659      +/-   ##
==========================================
- Coverage   83.16%   83.16%   -0.01%     
==========================================
  Files         277      277              
  Lines       48193    48193              
  Branches     9966     9910      -56     
==========================================
- Hits        40080    40078       -2     
+ Misses       7234     7218      -16     
- Partials      879      897      +18     

Flag	Coverage Δ
alpine320	75.16% <ø> (+<0.01%)	⬆️
fedora40	75.20% <ø> (+0.01%)	⬆️
macos-13	80.66% <ø> (+<0.01%)	⬆️
macos-14	80.66% <ø> (+<0.01%)	⬆️
macos-15	80.63% <ø> (ø)
mingw32	70.87% <ø> (-0.05%)	⬇️
mingw64	70.83% <ø> (-0.05%)	⬇️
npcap	85.30% <ø> (-0.02%)	⬇️
rhel94	75.05% <ø> (+0.02%)	⬆️
ubuntu2004	58.61% <ø> (-0.01%)	⬇️
ubuntu2004-zstd	58.75% <ø> (+0.01%)	⬆️
ubuntu2204	74.97% <ø> (+<0.01%)	⬆️
ubuntu2204-icpx	61.39% <ø> (-0.05%)	⬇️
ubuntu2404	75.20% <ø> (+<0.01%)	⬆️
unittest	83.16% <ø> (-0.01%)	⬇️
windows-2019	85.33% <ø> (-0.01%)	⬇️
windows-2022	85.36% <ø> (-0.01%)	⬇️
winpcap	85.33% <ø> (ø)
xdp	50.53% <ø> (+<0.01%)	⬆️

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