Add conversion and traceability for third-party test vectors

[sgmenda-aws]

Issues:

Addresses the need to convert third-party test vectors to AWS-LC's file_test.h format and track which vectors are tested. Currently, test vectors are manually converted and there's no systematic way to verify that all vectors in third_party/ are actually used in tests.

Description of changes:

Extends the test vector infrastructure from #2811 with two new phases (each can be skipped independently):

• Convert: Transforms Wycheproof JSON test vectors to file_test.h format via convert_vector.py (inspired by the existing Go converter)
• Spec: Generates vectors_spec.md with MUST requirements and uses duvet to verify that test files contain corresponding annotations

Converts and integrates aes_gcm_test from the latest upstream Wycheproof as a proof of concept, the test and duvet verification pass.

Call-outs:

• Conversion is Python-based (not Go) to keep tooling unified within the vectors system
• The existing Go converter at util/convert_wycheproof/ will be removed once all test vectors are migrated to the new system
• Also removes now-outdated aes_gcm_test vector in third_party/wycheproof_testvectors/
• Duvet verifies annotation presence but doesn't verify test coverage

Testing:

• Unit tests in convert_vector.py verify JSON to file_test.h conversion
• Tested full sync workflow and various skip flag combinations
• Verified error handling (invalid sources, missing files)
• Confirmed duvet correctly tracks annotation in crypto/cipher_extra/aead_test.cc

Run the full workflow with cd third_party/vectors && ./sync.py.

Run the migrated test with cd build && ./crypto/crypto_test --gtest_filter="AEADTest.WycheproofAESGCM"

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

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 78.42%. Comparing base (8009085) to head (977e313).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2839      +/-   ##
==========================================
+ Coverage   78.24%   78.42%   +0.17%     
==========================================
  Files         683      683              
  Lines      117346   117347       +1     
  Branches    16488    16492       +4     
==========================================
+ Hits        91821    92032     +211     
+ Misses      24641    24428     -213     
- Partials      884      887       +3     

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