[Request]: system property for default `--dns`.

Feature or enhancement request details

NOTE: Depends on #1425; there's no point tackling this until the TOML configuration is in place.

We've a number of issues relating to DNS resolution from containers not working properly when a third party DNS server conflicts with the server that macOS mDNSResponder wants to start.

Until an OS-level solution can be provided, it would be useful to have a system property (and potentially environment variables if session level overrides seem sensible) that allows the user to configure default values for --dns.

We can also consider properties for the other DNS CLI options here as well.

Code of Conduct

• I agree to follow this project's Code of Conduct