Reduce config validation message noise
What does this MR do?
Lowers the log level of informational config validation messages to info (from warning). And adds missing omitempty annotations to remove incorrect validation messages.
Why was this MR needed?
Config validation is too noisy and confusing.
What's the best way to test this MR?
Run with a deliberate config mistake (e.g. gitlab url of ""). You should see an info level warning about that field.