[WIP] [Hinty] Type hinting: layers

[gpotter2]

Note: after some experiments, Mypy will require so many changes that the files should be done one by one

Requires #2162

This PR:

• adds type hinting for scapy's layers

This was automatically generated, then reviewed manually. (STILL TODO) I may have missed some big mistakes, please review carefully. Note that the automatic detector tends to use specific Packet classes rather than the general "Packet" class.

Reviewers: it's a good idea to use the new "File viewed" feature 😄

[codecov]

Codecov Report

Merging #2164 into master will decrease coverage by 37.34%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master   #2164       +/-   ##
==========================================
- Coverage   87.34%     50%   -37.35%     
==========================================
  Files         200       5      -195     
  Lines       45451     128    -45323     
==========================================
- Hits        39699      64    -39635     
+ Misses       5752      64     -5688

Impacted Files	Coverage Δ
scapy/__init__.py	55.81% <ø> (-27.91%)	⬇️
scapy/compat.py	35.59% <0%> (-64.41%)	⬇️
scapy/consts.py	70.83% <0%> (-20.84%)	⬇️
scapy/contrib/ripng.py
scapy/arch/bpf/consts.py
scapy/contrib/spbm.py
scapy/plist.py
scapy/themes.py
scapy/layers/clns.py
... and 133 more