Common traits for ParsedPublicKey

[justsmth]

Issues:

Addresses #849

Description of changes:

Add several common traits (Send, Sync, Clone, and AsRef<[u8]>) for signature:: and agreement:: ParsedPublicKey.

Testing:

Tests updated.

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 96.15385% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 92.36%. Comparing base (c358484) to head (3b37f82).
⚠️ Report is 253 commits behind head on main.

Files with missing lines	Patch %	Lines
aws-lc-rs/src/signature.rs	88.88%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #879      +/-   ##
==========================================
- Coverage   95.80%   92.36%   -3.44%     
==========================================
  Files          61       73      +12     
  Lines        8143     9634    +1491     
  Branches        0     9634    +9634     
==========================================
+ Hits         7801     8898    +1097     
- Misses        342      450     +108     
- Partials        0      286     +286     

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[LukasKalbertodt]

I tested this patch in my project and it allowed me to replace my UnparsedPublicKeys with ParsedPublicKeys. Everything works as expected. Thank you :)

I also briefly looked over the code (as a non-maintainer, so I have zero authority here obviously) and it looks good!