[DONT MERGE] no-fragment-on-poly-hydration

[temaEmelyan]

Please make sure you consider the following:

• Add tests that use __typename in queries
• Does this change work with all nadel transformations (rename, type rename, hydration, etc)? Add tests for this.
• Is it worth using hints for this change in order to be able to enable a percentage rollout?
• Do we need to add integration tests for this change in the graphql gateway?
• Do we need a pollinator check for this?