Add CBOR fields (cborfields.py, cborpacket.py) and tests

[polybassa]

Checklist:

• If you are new to Scapy: I have checked CONTRIBUTING.md (esp. section submitting-pull-requests)
• I squashed commits belonging together
• I added unit tests or explained why they are not relevant
• I executed the regression tests (using tox)
• If the PR is still not finished, please create a Draft Pull Request

fixes #xxx

[codecov]

Codecov Report

❌ Patch coverage is 78.39644% with 97 lines in your changes missing coverage. Please review.
✅ Project coverage is 80.31%. Comparing base (f4a2ca4) to head (3011b60).
⚠️ Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
scapy/cbor/cborfields.py	77.85%	95 Missing ⚠️
scapy/cborpacket.py	89.47%	2 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff            @@
##           master    #4958    +/-   ##
========================================
  Coverage   80.30%   80.31%            
========================================
  Files         379      381     +2     
  Lines       93107    93556   +449     
========================================
+ Hits        74769    75136   +367     
- Misses      18338    18420    +82     

Files with missing lines	Coverage Δ
scapy/cbor/__init__.py	100.00% <100.00%> (ø)
scapy/cborpacket.py	89.47% <89.47%> (ø)
scapy/cbor/cborfields.py	77.85% <77.85%> (ø)

... and 9 files with indirect coverage changes

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