fix: removes unwrap from is_federated query

[EverlastingBugstopper]

Fixes #548 by removing the .unwrap call in the is_federated run that occurs if anything goes wrong with the query (for instance, mistyping your graph name).

This PR includes a few other refactors:

• No longer run the is_federated check if the --convert flag is passed to subgraph publish, removing the extra network hop
• Perform the is_federated query directly in the rover_client::query modules that need them, instead of in rover code.
  • This includes returning RoverClientError::ExpectedFederatedGraph directly from rover_client instead of constructing the error manually in rover
  • We still keep the suggestion for using --convert 😄
• Replaced some verbose matches with a more ergonomic .ok_or

Also fixes #550

[EverlastingBugstopper]

this should be !is_federated