codegen: Generate @lazy fields with abstract effect

[johnspade]

Hello!

We use a heavily customized version of the Caliban code generator at $Work and would like to contribute back some of our changes. Caliban recently added support for the @lazy directive, the point of this PR is to improve its support for code with abstract effect (F[_]). Codegen currently generates code that won't compile due to a missing abstract type parameter in case classes:

type Foo {
  bar: String!
  baz: String! @lazy
}

object Types {
  final case class Foo(bar: String, baz: F[String])
}

This PR adds a couple tests and changes for object and nested lazy fields generation.

[ghostdogpr]

Thanks for the improvements!