Multiple Queries in a Request Async

### Problem/Solution

Looking for a way to run multiple queries in a request, but have them processed asynchronously.

According to the docs, this can only happen sequentially making GraphQL plugins like BatchHttpLink inefficient: https://hasura.io/docs/latest/queries/postgres/multiple-queries/

No implementation files or tests are identified. Start with the linked multiple-queries documentation and the GraphQL request path, then determine how multiple queries are currently processed and where asynchronous execution could be introduced. Done means multiple queries in one request can execute asynchronously rather than only sequentially, supporting clients such as BatchHttpLink.

Written by the indexing model from the issue text.