feat(lambda-events): add VPC Lattice event structures

[andrewpatto]

📬 Issue #, if available:

#1028

✍️ Description of changes:

Added event structures for the VPC lattice service - including tests and sample request/responses.

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• I confirm that I've ran cargo +nightly fmt.
• I confirm that I've ran cargo clippy --fix.
• I confirm that I've made a best effort attempt to update all relevant documentation.
• I confirm that my contribution is made under the terms of the Apache 2.0 license.