aws: add sigv4/a test corpuses

[nbaws]

This patch adds around 160 test cases based on the aws signer test corpus from https://github.com/awslabs/aws-c-auth/tree/main/tests/aws-signing-test-suite

Adding these test cases uncovered the following bugs, which have also been fixed in this patch:

• Incorrect handling of UTF8 encoded parameters
• Incorrect date calculation (missing seconds from the date formatter)
• Invalid handling of tilde within query parameters (also reported by Animal Logic leading to this patch)

Commit Message: aws: add sigv4/a test corpuses
Additional Description:
Risk Level: Low
Testing: Unit
Docs Changes:
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