[DRAFT] Serialization for kem::DecapsulationLey

[justsmth]

Issues:

Addresses #799

Description of changes:

TBD

Call-outs:

TBD

Testing:

TBD

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license and the ISC license.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 73.87387% with 29 lines in your changes missing coverage. Please review.
✅ Project coverage is 92.20%. Comparing base (c358484) to head (54f9d2b).
⚠️ Report is 266 commits behind head on main.

Files with missing lines	Patch %	Lines
aws-lc-rs/src/kem.rs	73.87%	28 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #908      +/-   ##
==========================================
- Coverage   95.80%   92.20%   -3.60%     
==========================================
  Files          61       73      +12     
  Lines        8143     9765    +1622     
  Branches        0     9765    +9765     
==========================================
+ Hits         7801     9004    +1203     
- Misses        342      474     +132     
- Partials        0      287     +287     

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