fix(core): don't consider queries as enabled if they have no observers and have never fetched (successfully or erroneously) (#8161)

it's very likely that this used to be a disabled observer; one other case would be canceling a query while you were initially fetching it, but this is a weird corner case that brings all sorts of troubles

additionally, we can check for the queryFn being a skipToken; even if we have data in the cache, when the queryFn is currently set to skipToken, this is means we never want to see this query fetch