Use GraphQLSchema to speed up schema parsing.

[stephenh]

Visiting DocumentNode directly was fairly tedious because there was
no map-based access to the types, so each time we wanted to look
up the type of a field/argument/etc., we had to start all over
at the top and rescan the AST (specifically extractTypeDefinition).

This adds a new GraphQLTypes to source-helper that is the trio
of types/unions/enums that is: a) built quickly via the graphql's
buildASTSchema, and b) built once up-front in parse.ts
and then replaces DocumentNode as what we pass around as our
current schema.

[stephenh]

Updated to not pull in graphql-tools but instead use the same buildASTSchema primitive from graphql that the makeExecutableSchema was using.

[Weakky]

Hey there 👋,

Thanks for this awesome PR. It looks like there are problems with GraphQLList and possibly with GraphQLNonNull types.

This is what the generated graphqlgen.ts file looks like on your PR:

Notice the => {}[] | Promise<{}[]> which is supposed to be of return type => Post[] | Promise<Post[]>

It looks like the GraphQLList types do not have any name property defined.

Would you mind fixing this issue, and making sure that the output of the yoga template is the same as before?

Thanks 🙏

[Weakky]

Bug should be fixed in ce962ab

[stephenh]

Ha, nice! I'd just noticed the {} in our schema last night as well, and realized what you did, that a list + a non-null wasn't being traversed across the two hops to the final type. Thanks for the merge + clean up!