Implement Declarative Auth Design for ballerina/http Module

[ldclakmal]

Purpose

This PR introduces the declarative auth design for HTTP listener.

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

Example:

import ballerina/http;
 
@http:ServiceConfig {
   auth: [
      {
         jwtValidatorConfig: {
            issuer: "ballerina",
            audience: ["wso2"],
            jwksConfig: {
               url: "https://localhost:8080/jwks"
            }
         },
         scopes: ["update", "write"]
      },
      {
         introspectionConfig: {
            url: "https://localhost:9090/oauth2/introspect",
            tokenTypeHint: "access-token",
            clientConfig: {
               auth: { username: "tom", password: "123" },
               secureSocket: {
                  trustStore: {
                     path: "/path/to/truststore.p12",
                     password: "ballerina"
                  }
               }
            }
         },
         scopes: ["update", "write"]
      }
   ]
}
service http:Service /hello on new(9090) {
   resource function post /foo(json payload) returns string {
       // business logic
   }
}

Fixes ballerina-platform/ballerina-library#813
Fixes ballerina-platform/ballerina-library#74

Related to ballerina-platform/ballerina-library#584