Missing and/or empty Query

[simunic-cz]

When:

• no Query is defined in the GQL schema, deployment fails with error There is no top level schema object defined.
  AppSync does not pickup the Mutation, nor Subscription operations without the Query operation being present as well.
• the GQL schema is explicitly defined without the Query operation, deployment fails with error A schema MUST have a 'query' operation defined.
• the GQL schema is explicitly defined with empty Query operation, then the „Queries“ page in AppSync API console fails to load

Bugs reproduction

All 3 scenarios are demonstrated in this bug reproduction here: https://github.com/testuj-to/appsync-missing-query