Propagate opts configured in prepare_query/3 to preloads

This ensures that when `:on_preloader_spawn` is set in the
`prepare_query/3` callback, it is propagated to the preloader.

Author: derekkraan

lib/ecto/repo/queryable.ex

@@ -217,6 +217,7 @@ defmodule Ecto.Repo.Queryable do
     %{adapter: adapter, cache: cache, repo: repo} = adapter_meta
 
     {query, opts} = repo.prepare_query(operation, query, opts)
+    tuplet = {adapter_meta, opts}
     query = attach_prefix(query, opts)
 
     {query_meta, prepared, cast_params, dump_params} =