Fix websocket authorizers data located in wrong place

[DocLM]

Move authorizer and identity data to requestContext in order to follow lambda proxy specs.

Description

This pull request fix a wrong identity and authorizer informations contained in the lambda event instead of requestContext object

Relates to #1379

Motivation and Context

This fix a wrong behaviour for lambda and websocket authorizers.
Authorizer and identity data should be inside requestContext object when used with lambda proxy (like serverless-offline does)

https://docs.aws.amazon.com/apigateway/latest/developerguide/api-gateway-lambda-authorizer-output.html
https://docs.aws.amazon.com/apigateway/latest/developerguide/set-up-lambda-proxy-integrations.html

In particular a reference to:

For the Lambda proxy integration, API Gateway passes the context object from a Lambda authorizer directly to the backend Lambda function as part of the input event. You can retrieve the context key-value pairs in the Lambda function by calling $event.requestContext.authorizer.key.

Also integrated changes from #1376 in order to adhere to AWS behaviour: https://docs.aws.amazon.com/apigateway/latest/developerguide/api-gateway-lambda-authorizer-output.html

You can access the stringKey, numberKey, or booleanKey value (for example, "value", "1", or "true") of the context map in a mapping template by calling $context.authorizer.stringKey, $context.authorizer.numberKey, or $context.authorizer.booleanKey, respectively. The returned values are all stringified. Notice that you cannot set a JSON object or array as a valid value of any key in the context map. 

How Has This Been Tested?

Detected the difference between AWS and serverless-offline
Reflect the changes in current websocket tests in order to catch the behaviour change

Screenshots (if appropriate):

[dnalborczyk]

thank you @DocLM !