Further generalize Xi's changes

- introduce a slightly more general notion of an AutoRouted provider
- the AutoRouted provider is associated with a RoutingTable provider
- e.g. inference -> models
- Introduced safety -> shields and memory -> memory_banks
  correspondences

llama_stack/apis/shields/__init__.py

@@ -0,0 +1,7 @@
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+# All rights reserved.
+#
+# This source code is licensed under the terms described in the LICENSE file in
+# the root directory of this source tree.
+
+from .shields import *  # noqa: F401 F403