impl AsDer<PublicKeyX509Der<'static>> for ParsedPublicKey

[justsmth]

Issues:

Addresses: #849 (comment)

Description of changes:

Allows the encoding of a ParsedPublicKey into an X509 public key.

Call-outs:

verify_sig and verify_digest_sig in RsaParameters was assuming an RFC8017 encoded public key. I don't see any reason that it should not also accept X509.

Testing:

Updated tests to provide coverage.

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 50.00000% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 92.35%. Comparing base (c358484) to head (31547d0).
⚠️ Report is 260 commits behind head on main.

Files with missing lines	Patch %	Lines
aws-lc-rs/src/rsa/signature.rs	0.00%	0 Missing and 2 partials ⚠️
aws-lc-rs/src/signature.rs	75.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #885      +/-   ##
==========================================
- Coverage   95.80%   92.35%   -3.45%     
==========================================
  Files          61       73      +12     
  Lines        8143     9638    +1495     
  Branches        0     9638    +9638     
==========================================
+ Hits         7801     8901    +1100     
- Misses        342      450     +108     
- Partials        0      287     +287     

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