Use graphql-java's TypeUtil to unwrap and print SDL types - #871

Checklist

• Pull requests follows the contribution guide
• New or modified functionality is covered by tests

Description

Our Type<*>.unwrap() returned Type<*>, so most callers cast the result to TypeName even though an unwrapped SDL type is always a TypeName. It now returns TypeName through graphql-java's TypeUtil.unwrapAll, which drops those casts and a !is TypeName check that could never be true.

Same thing in UnmappedInputFieldChecker#inputObjectOf: GraphQLTypeUtil.unwrapAllAs can return a GraphQLNamedType directly since every unwrapped schema type has a name, type references included.

TypeUtil isn't annotated @PublicApi, but it's been in graphql-java since at least 20.0.

The only behaviour change is the type matcher's error message, which now prints the SDL type with TypeUtil.simplePrint. For a [Book!]! field whose resolver returns a single Book:

Unable to match type definition (NonNullType{type=ListType{type=NonNullType{type=TypeName{name='Book'}}}}) for reference ...

becomes

Unable to match type definition ([Book!]!) for reference ...

GraphQLTypeUtil itself didn't help much elsewhere since most of our code works on SDL types, not schema types.

mvn clean verify passes against graphql-java 26.1 and 25.1. I also ran every verify-tools scenario on this branch and on master: same schemas, results and logs, except the error message above.