deps(apigateway): migrate client to use v3.

[Hweinstock]

Problem

client still uses v2.

Solution

• Very straightforward migration, mostly exchanging types.

Verification

• Create a simple APIGateway that redirects to a GET request to this repo's homepage.
• Use the invoke method from the IDE.
• Copy ARN, name, and URL.

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• Treat all work as PUBLIC. Private feature/x branches will not be squash-merged at release time.
• Your code changes must meet the guidelines in CONTRIBUTING.md.
• License: I confirm that my contribution is made under the terms of the Apache 2.0 license.