Inline Fragment Support for Ballerina GraphQL

[ThisaruGuruge]

Description:
Currently, the Ballerina GraphQL package only supports named fragmeents. It should support inline fragments.

For an example, the following query should be valid:

query {
    ... on Query {
        profile {
            name
        }
    }
}

on the following service:

import ballerina/graphql;

service graphql:Service on new graphql:Listener(9090) {
    resource function get profile returns Person {
        return { name: "John Doe", age: 20 };
    }
}

type Person record {
    string name;
    int age;
};

Part of #1224