Access to public `ParsedDocument`

[xuorig]

A ParsedDocument is currently available in extensions (https://github.com/apollographql/router/blob/c96bbee21343a456e49da231aa218a316da32dda/apollo-router/src/services/layers/query_analysis.rs#L161-L169)

However both the type alias and ParsedDocumentInner are pub(crate).

It would be very useful for plugins to be able to retrieve the apollo-compiler structures (which are all public themselves). We have multiple use cases where we need to peak into the query to analyse it and parsing it every time is an issue.