Force package search during unit test ref resolution to only look at …

…package of unit test

This is necessary because when we create the shadow manifest for the running
the unit test node, the included models whether direct or external, get rewritten
as being in the unit test's package.

core/dbt/context/providers.py

@@ -578,7 +578,7 @@ def resolve(
         target_version: Optional[NodeVersion] = None,
     ) -> RelationProxy:
         target_name = f"{self.model.name}__{target_name}"
-        return super().resolve(target_name, target_package, target_version)
+        return super().resolve(target_name, self.model.package_name, target_version)
 
 
 # `source` implementations