Test(generator): Add unit tests for Prisma to GraphQL schema conversion

[Sylvain]

Simple CRUD operations:

• get<Model>
• list<Model>
• count<Model>
• create<Model>
• createMany<Model>
• update<Model>
• updateMany<Model>
• upsert<Model>
• delete<Model>
• deleteMany<Model>

Advanced operations:

• Nested read
• Deeply nested read
• Nested write
• Relation filter (relation to one)
• Relation filter (relation to many)
• Custom resolver

Not supported (yet):

• Deeply nested write
• Deeply nested relation filters