Monitor mode docs

[gpotter2]

This PR:

• removes automatic setter of monitor mode on Linux, as it resets the networking card without any warning. The utiles remain, but it should have been a user decision.
• Add troubleshooting doc for monitor mode

[codecov]

Codecov Report

Merging #2028 into master will decrease coverage by <.01%.
The diff coverage is 0%.

@@            Coverage Diff             @@
##           master    #2028      +/-   ##
==========================================
- Coverage   86.35%   86.35%   -0.01%     
==========================================
  Files         196      196              
  Lines       44339    44338       -1     
==========================================
- Hits        38290    38286       -4     
- Misses       6049     6052       +3

Impacted Files	Coverage Δ
scapy/arch/linux.py	74.74% <0%> (+0.18%)	⬆️
scapy/autorun.py	78.51% <0%> (-4.14%)	⬇️
scapy/layers/tls/handshake_sslv2.py	91.32% <0%> (-1.89%)	⬇️
scapy/sendrecv.py	85.1% <0%> (-0.34%)	⬇️
scapy/asn1/ber.py	83.09% <0%> (+0.28%)	⬆️
scapy/automaton.py	82.36% <0%> (+0.55%)	⬆️
scapy/layers/tls/record.py	92.1% <0%> (+0.87%)	⬆️

[gpotter2]

@guedou @p-l- This is ready for reviewing !