feat(persisted): Replace persistedFetchExchange with generic persistedExchange

[kitten]

Resolves #2988
Resolves #2989

Summary

This change modifies @urql/core/internal to know how to modify FetchBody according to the (Automatic) Persisted Queries specification, leaving out query as needed.

The persistedExchange replaces persistedFetchExchange and hence also now works with third-party transports and the subscriptionExchange.

Types have been added to @urql/core to reflect the extensions.persistedQuery spec, with an added miss?: boolean field, which is set when query must be included again (i.e. when a persisted query "misses", via APQ)

The persistedExchange must hence now be placed in front of the default fetch exchange, and/or in front of a subscriptionExchange that handles queries.

The package has been renamed to @urql/exchange-persisted to reflect this.

Set of changes

• Rename @urql/exchange-persisted-fetch to @urql/exchange-persisted
• Add persistedQuery types to extensions on @urql/core
• Handle omitting query in makeFetchBody
• Implement persistedExchange replacing persistedFetchExchange with generic retry logic

[kitten]

We'll have to decide what to do with @urql/exchange-multipart-fetch. I reckon, we remove it from the repository after a release. As for @urql/exchange-persisted-fetch, it'll likely just continue to work, as normal, after this is merged and released, so similarly there's no actionable after it's removed when this PR is merged.