feat(appsec): publish response body on end invocation

[CarlesDD]

What does this PR do?

Publishes the Lambda response body, headers and base64 flag on the datadog:lambda:end-invocation diagnostic channel, so the tracer can extract an API Security schema for server.response.body. This is the last missing piece of the response-body feature, request body and headers were already published.

Motivation

Closes the response-body gap in API Security for AWS Lambda

Testing Guidelines

• npx jest src/appsec/ src/trace/: 28 suites, 516 tests, all green.
• Verified end to end locally: built this layer and the paired dd-trace-js branch (#10138) into a real Lambda layer with the Docker/RIE harness, and ran system-tests. Test_Schema_Response_Body passes on both.

Additional Notes

Types of Changes

• Bug fix
• New feature
• Breaking change
• Misc (docs, refactoring, dependency upgrade, etc.)

Check all that apply

• This PR's description is comprehensive
• This PR contains breaking changes that are documented in the description
• This PR introduces new APIs or parameters that are documented and unlikely to change in the foreseeable future
• This PR impacts documentation, and it has been updated (or a ticket has been logged)
• This PR's changes are covered by the automated tests
• This PR collects user input/sensitive content into Datadog
• This PR passes the integration tests (ask a Datadog member to run the tests)

APPSEC-68936