Use Custom DNS Servers

We're modern progressive parents and aren't about to tell Vector who it can and can't hang out with. As such, we're now allowing you to specify custom DNS servers in your configs.

The configuration isn't complicated, it's a global array field dns_servers:

dns_servers: ["0.0.0.0:53"]

When dns_servers is set Vector will ignore the system configuration and use only the list of DNS servers provided.