DCE/RPC: various bug fixes in PKT_PRIVACY mode / client fragmentation

[gpotter2]

• add client fragmentation
• move DCE/RPC defragmentation after the decryption/integrity check
• fix vt_trailer parsing when packet encryption is used
• improve error logging when DCE/RPC fails to be parsed
• fix request/response association when passively sniffing an encrypted pcap

(yeah.. currently we tried to reassemble encrypted chunks -_-)

[codecov]

Codecov Report

Attention: Patch coverage is 69.29825% with 35 lines in your changes missing coverage. Please review.

Project coverage is 82.11%. Comparing base (7275516) to head (b226b7c).
Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
scapy/layers/dcerpc.py	69.38%	30 Missing ⚠️
scapy/layers/smbclient.py	58.33%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4664      +/-   ##
==========================================
+ Coverage   81.90%   82.11%   +0.21%     
==========================================
  Files         359      359              
  Lines       86574    86615      +41     
==========================================
+ Hits        70909    71126     +217     
+ Misses      15665    15489     -176     

Files with missing lines	Coverage Δ
scapy/layers/msrpce/rpcclient.py	52.27% <100.00%> (+0.21%)	⬆️
scapy/layers/smb2.py	88.11% <100.00%> (+0.03%)	⬆️
scapy/layers/smbclient.py	73.96% <58.33%> (-0.16%)	⬇️
scapy/layers/dcerpc.py	90.57% <69.38%> (-0.86%)	⬇️

... and 24 files with indirect coverage changes