Upgrade axum from 0.5.x to 06.x, and axum-macros from 0.2.x to 0.3.x

[hansonchar]

Description of changes:

Changes based on the guidance of the axum CHANGELOG.md.

Tests passed using the aws-kms-xksproxy-test-client.

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• [ ] Were any files moved? Moving files changes their URL, which breaks all hyperlinks to the files.