Simplify get_namespace() and adjust get_and_report_namespace() method signature

[Salvo Polizzi]

Following the last discussion in ​PR, we propose the following improvements to enhance readability and reduce confusion:

1. Simplify get_namespace():
   • The current implementation of get_namespace() can be rewritten as a one-liner for better readability without changing its functionality.
   • Example:

     #current
     def get_namespace(self):
             apps_models = apps.get_models()
             namespace = {}
             for model in reversed(apps_models):
                 if model.__module__:
                     namespace[model.__name__] = model
             return namespace
     
     #proposed
     def get_namespace():
             return {m.__name__: m for m in reversed(apps.get_models()) if m.__module__}
     

2. Update get_and_report_namespace():
   • The no_imports parameter in the method signature can be misleading and cause confusion for its users.
   • Proposed Change: Remove the no_imports parameter from the method and instead handle its logic in the relevant runners where the namespace is imported.
   • Justification: This improves separation of concerns and makes the method more focused.