Move object storage account_client to lib interface

object storage account_client is stable now and good to be moved
as stable library interface.

Partially implements blueprint consistent-service-method-names

Change-Id: I03863fbb23e914b4115f2c0aaec0ecf266ccc060
diff --git a/releasenotes/notes/make-account-client-as-stable-interface-d1b07c7e8f17bef6.yaml b/releasenotes/notes/make-account-client-as-stable-interface-d1b07c7e8f17bef6.yaml
new file mode 100644
index 0000000..9d5a1f5
--- /dev/null
+++ b/releasenotes/notes/make-account-client-as-stable-interface-d1b07c7e8f17bef6.yaml
@@ -0,0 +1,9 @@
+---
+features:
+  - |
+    Define below object storage service clients as libraries.
+    Add new service clients to the library interface so the
+    other projects can use these modules as stable libraries
+    without any maintenance changes.
+
+      * account_client