Split aws-lambda-nodejs into construct and bundler, and expose bundler

[nihakue]

At the moment, it's very difficult to use aws-lambda-nodejs along with other high level lambda function constructs (such as Lambda@Edge) because they both subclass lambda.Function. The vast majority of the benefit of using aws-lambda-nodejs is the bundler, so it seems like it should be possible to make it available independent of the construct. @jogold do you have any thoughts on this?

In general, is there a best practice pattern for extending L2 constructs in a way that doesn't make them mutually exclusive with other L2 construct extensions? I'm thinking along the lines of plugins, mixins, composition, that sort of thing.

[indrora]

Generally, duplication of the construct and refactoring out the shared code between them would be a preferred mechanism.

Splitting out the bundler would have other, possibly positive effects as well. How would you define this interface?