Introduce BackendStateLifecycle abstraction

This replaces StateLifecycle.
The concept of assets is removed from the API. Each services that does
operations with the state handles the level of persistence to support
(and therefore, the deep persistence)

localstack/services/plugins.py

@@ -133,11 +133,26 @@ def on_exception(self):
         pass
 
 
-class StateLifecycle:
-    def retrieve_state(self):
-        pass
+class BaseBackendStateLifecycle(abc.ABC):
+    """
+    Interface that supports the retrieval, injection and restore of the backend for services.
+    """
+
+    @abc.abstractmethod
+    def retrieve_state(self, **args):
+        """Retrieves a backend for an account, region and service"""
 
-    def inject_state(self, state):
+    @abc.abstractmethod
+    def inject_state(self, **args):
+        """Injects a backend for an account, region and service"""
+
+    @abc.abstractmethod
+    def reset_state(self):
+        """Resets a backend for an account, region and service"""
+
+    @abc.abstractmethod
+    def on_after_reset(self):
+        """Performed after the reset of a service"""
         pass
 
 
@@ -151,7 +166,7 @@ def __init__(
         active=False,
         stop=None,
         lifecycle_hook: ServiceLifecycleHook = None,
-        state_lifecycle: StateLifecycle = None,
+        backend_state_lifecycle: BaseBackendStateLifecycle = None,
     ):
         self.plugin_name = name
         self.start_function = start
@@ -160,7 +175,7 @@ def __init__(
         self.default_active = active
         self.stop_function = stop
         self.lifecycle_hook = lifecycle_hook or ServiceLifecycleHook()
-        self.state_lifecycle = state_lifecycle
+        self.backend_state_lifecycle = backend_state_lifecycle
         call_safe(self.lifecycle_hook.on_after_init)
 
     def start(self, asynchronous):