Issue 50390 - Add Managed Entries Plug-in Config Entry schema
    
    Description: Add AttributeTypes and an ObjectClass to Managed Entries
    Plug-in Configuration entry schema.
    Fix MEPConfigs(DSLdapObjects) accordingly.
    
    https://pagure.io/389-ds-base/issue/50390
    
    Reviewed by: mreynolds (Thanks!)
    
    (cherry picked from commit 31c89d3bbd0bcfea71b4e6be912ad4bb9f43e171)