mysql: Use separate file for secret + remove duplicated mysql name

mysql/kustomize/overlays/default/kustomization.yaml

@@ -26,10 +26,9 @@ patches:
 - path: replica.yaml
 
 configMapGenerator:
-- name: mysql-configmap
+- name: configmap
   env: mysql-configmap.properties
 
 secretGenerator:
-- name: mysql-secret
-  literals:
-  - mysql-root-password=root
+- name: secret
+  env: mysql-secret.properties