Implement Imperative Auth Design for ballerina/http Module

[ldclakmal]

Purpose

This PR introduces the imperative auth design for HTTP listener. Also, imperative and declarative auth design for HTTP client.

Design: https://docs.google.com/document/d/1dGw5uUP6kqZNTwMfQ_Ik-k0HTMKhX70XpEA3tys9_kk/edit?usp=sharing

Example:

import ballerina/http;
import ballerina/jwt;
 
http:JwtValidatorConfig config = {
   issuer: "ballerina",
   audience: ["wso2"],
   jwksConfig: {
      url: "https://localhost:8080/jwks"
   },
   scopeKey: "scp"
};
http:ListenerJwtAuthHandler handler = new(config);
 
service http:Service /hello on new(9090) {
   resource function post /foo(json payload, @Header string authorization) 
                               returns string|http:Unauthorized|http:Forbidden {
 
      jwt:Payload|http:Unauthorized authn = handler.authenticate(authorization);
      if (authn is http:Unauthorized) {
         return authn;
      }
 
      http:Forbidden? authz = handler.authorize(<jwt:Payload>authn, "write");
      if (authz is http:Forbidden) {
         return authz;
      }
 
      // business logic
   }
}

Fixes ballerina-platform/ballerina-library#752
Fixes ballerina-platform/ballerina-library#553
Fixes ballerina-platform/ballerina-library#63

Related to ballerina-platform/ballerina-library#584