feat: Support module concat in middleware to avoid compile-time dependencies

[axelson]

This allows using Module.concat/1,2 to provide the middleware. The benefit of this is that the resolver no longer has a compile-time dependency on the middleware, and more importantly a transitive dependency on all the middleware's runtime dependencies.

Here is an example of a supported field definition:

field :folder, non_null(:folder) do
  arg :id, non_null(:string)
  middleware Module.concat(MyAppWeb.GraphQL, MyMiddleware), some_options: [42]
  resolve &SomeResolver.project_folder/3
end

This almost works today, but MyMiddleware doesn't receive the provided options.

Fix is related to #1359

This is more of a PoC/RFC right now. We may actually want to go with an approach that targets the compiler directly, like these two related ecto commits:

• Disable lexical tracker for association modules elixir-ecto/ecto#1670
• elixir-ecto/ecto@cadaced

[s3cur3]

I am extremely interested in this fix for @Jump-App's codebase. Right now the compile-time dependencies via our Absinthe schema means any change to what is conceptually a leaf module results in 30+ modules being recompiled. If there's anything I can do to help, let me know.

[cschiewek]

I'd be much more in favour of handling it via the compiler. Module.concat is hacky.