Add CBOR codec and BPv7 packet classes

[BrianSipos]

This change addresses #4874 by adding new base scapy classes to encode and decode CBOR structure RFC 8949. This is in support of a new protocol support for BPv7 RFC 9171. This work was adapted from earlier out-of-source additions from dtn-demo-agent.

Both include a minimal set of unit tests to cover normal behavior. Since this is focused on immediate needs for BPv7 the CBOR fields and packets are not exhaustive.

Fixes #4874

[polybassa]

@BrianSipos Thanks a lot for this PR.

Please have a look at the failing tests.

I would also recommend to move the CBOR implementation into "contrib".

[codecov]

Codecov Report

❌ Patch coverage is 18.70702% with 591 lines in your changes missing coverage. Please review.
✅ Project coverage is 48.00%. Comparing base (3255441) to head (a5b8d37).
⚠️ Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
scapy/contrib/bpv7.py	0.44%	225 Missing ⚠️
scapy/cbor.py	23.52%	208 Missing ⚠️
scapy/cborfields.py	30.90%	114 Missing ⚠️
scapy/cborpacket.py	27.86%	44 Missing ⚠️

❗ There is a different number of reports uploaded between BASE (3255441) and HEAD (a5b8d37). Click for more details.

HEAD has 10 uploads less than BASE

Flag	BASE (3255441)	HEAD (a5b8d37)
	12	2

Additional details and impacted files

@@             Coverage Diff             @@
##           master    #4875       +/-   ##
===========================================
- Coverage   80.87%   48.00%   -32.88%     
===========================================
  Files         368      354       -14     
  Lines       90262    90663      +401     
===========================================
- Hits        72998    43521    -29477     
- Misses      17264    47142    +29878     

Files with missing lines	Coverage Δ
scapy/all.py	100.00% <100.00%> (ø)
scapy/cborpacket.py	27.86% <27.86%> (ø)
scapy/cborfields.py	30.90% <30.90%> (ø)
scapy/cbor.py	23.52% <23.52%> (ø)
scapy/contrib/bpv7.py	0.44% <0.44%> (ø)

... and 320 files with indirect coverage changes

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[BrianSipos]

@polybassa one need for BPv7 is a CRC-16 and CRC-32C generator. Right now this uses crcmod package, which has not been updated in a while but is still recent Python compatible. Do you have any preference about how to generate CRC values? I don't see other packages used from other protocols in scapy.