Implement DTLS 1.3 record layer encoding

[JoTurk]

Description

POC for my interface idea for dtls 1.3 record layer encoding #755 has some code copied from #793 I'm going to clean it and make the DTLS 1.3 and DTLS 1.2 paths explicit after 793. Not ready for review right now.

resolves #755

[codecov]

Codecov Report

❌ Patch coverage is 68.22917% with 61 lines in your changes missing coverage. Please review.
✅ Project coverage is 82.13%. Comparing base (d7a09d4) to head (76ca03d).

Files with missing lines	Patch %	Lines
pkg/protocol/recordlayer/recordlayer_13.go	66.37%	23 Missing and 15 partials ⚠️
pkg/protocol/recordlayer/header_13.go	66.66%	17 Missing and 6 partials ⚠️

❌ Your patch check has failed because the patch coverage (68.22%) is below the target coverage (70.00%). You can increase the patch coverage or adjust the target coverage.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #833      +/-   ##
==========================================
- Coverage   82.47%   82.13%   -0.35%     
==========================================
  Files         121      124       +3     
  Lines        6928     7119     +191     
==========================================
+ Hits         5714     5847     +133     
- Misses        803      842      +39     
- Partials      411      430      +19     

Flag	Coverage Δ
go	82.13% <68.22%> (-0.35%)	⬇️

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[theodorsm]

Let me know when it's ready for review! I merged #793, I hope that doesn't create too many conficts, or if you had other plans.