Add events for CDK custom resource provider framework.

[mawallace]

Description of changes:

There is a CDK custom resource provider framework which makes writing custom resource lambdas easier.

This adds the request/response types for lambdas used in this framework.

By submitting this pull request

• I confirm that my contribution is made under the terms of the Apache 2.0 license.
• I confirm that I've made a best effort attempt to update all relevant documentation.

[calavera]

Thanks a lot!