Inline fragment type conditions are not added to used types

[martinbonnin]

Description

query myQuery {
    getMyI() {
        ... on A { .... }
        ... on B { .... }
    }
}

A and B are not generated in $packageName.type. This is because historically, the minimum amount of information was stored there and this grew up progressively to store cache-related information (key fields, etc...).

We should either add those or provide a better "schema" API for clients who want to use those types.