Add support for Request Lambda Event Payload Authorizers

@app.authorizer once deployed creates a new authorizer that is using `Token` in the Lambda event handler options.

Adding a new authorizer (or extending the existing ChaliceAuthorizer) that would be able to create the one with `Request` option would be greatly beneficial:
1) this type of authorizer provide much more flexibility in terms of authorizing request
2) from what I see the WebSockets authorizers utilizes this kind of authorizer, so it could be the first step of resolving https://github.com/aws/chalice/issues/1457

With some guidance I could possibly start working on this

Start with the @app.authorizer entry point and the existing ChaliceAuthorizer implementation, then review how Lambda event handler options select Token authorizers. Check the related WebSockets authorizer behavior and issue #1457 for context. Done means an authorizer can be created with the Request option while preserving existing Token behavior.

Written by the indexing model from the issue text.