Removes Backend class and moves logic and free functions to Launch file, updates tests

Author: Grace Kalu-Anyah

src/fastcs/attributes.py

@@ -65,7 +65,7 @@ async def update(self, attr: AttrR) -> None:
 class Attribute(Generic[T]):
     """Base FastCS attribute.
 
-    Instances of this class added to a ``Controller`` will be used by the backend.
+    Instances of this class added to a ``Controller`` will be used by the FastCS class.
     """
 
     def __init__(