add query root in mutation fields

[rakeshkky]

Support queries in mutation response.

Example:-

    mutation insert_article {
      insert_article(
        objects: [
          {
            id: 21,
            title: "Article 1",
            content: "Sample article content",
            author_id: 3
          }
        ]
      ) {
        returning {
          id
          title
        }
        query {
          author(where: {id: {_eq: 1}){
            id
            name
          }
        }
      }
    }

[0x777]

Blocked on #1576

[manasag]

This issue will now be reviewed and tracked as part of the Hasura V3 roadmap.

[beepsoft]

@manasag, is this still on the V3 roadmap?