fix: async behaviour

[saileshkotha]

Description Removed logic where async changes the integration to AWS Added logic to ignore the result of lambda and return a 200 Added body parsing (it parses both application/x-www-form-urlencoded and application/json). Motivation and Context https://www.serverless.com/framework/docs/providers/aws/events/apigateway#using-asynchronous-integration

Fixes the behavior of adding the async option to HTTP events.

When async is added, the API Gateway should auto-respond with a 200 and then invoke the lambda asynchronously with the same event as a regular lambda proxy event as described in the docs above.

How Has This Been Tested? Unit Test Running Locally

[saileshkotha]

@dherault Can you please approve the running workflow? We fixed tests in the current branch. We need the async behavior in our projects.

[dnalborczyk]

close/re-open in order to run ci.