Migrate the dynamic creds module to tempest lib

This commit migrates the dynamic credentials provider from
tempest/common into tempest/lib.

Change-Id: Id8d60e4d7c22bc72c3e48bc768509ff0cc0c89d5
diff --git a/releasenotes/notes/migrate-dynamic-creds-ecebb47528080761.yaml b/releasenotes/notes/migrate-dynamic-creds-ecebb47528080761.yaml
new file mode 100644
index 0000000..c20cbc6
--- /dev/null
+++ b/releasenotes/notes/migrate-dynamic-creds-ecebb47528080761.yaml
@@ -0,0 +1,5 @@
+---
+features:
+  - |
+    The tempest module tempest.common.dynamic creds which is used for
+    dynamically allocating credentials has been migrated into tempest lib.