Add option and defaults to configure metrics exporting in containerd (#5466)

* Add metrics exporting in containerd config

* Add containerd.yml with containerd configuration example to the sample group_vars

inventory/sample/group_vars/all/containerd.yml

@@ -0,0 +1,15 @@
+---
+# Please see roles/container-engine/containerd/defaults/main.yml for more configuration options
+
+# containerd_config:
+#   grpc:
+#     max_recv_message_size: 16777216
+#     max_send_message_size: 16777216
+#   debug:
+#     level: ""
+#   registries:
+#     "docker.io": "https://registry-1.docker.io"
+#   max_container_log_line_size: -1
+#   metrics:
+#     address: ""
+#     grpc_histogram: false