Not convenient to call bind_with_addr to make a AsyncResolver

[hainesc]

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Maybe I have missed something, but AFAIK, it is not convenient to call bind_with_addr when I want to make dns resolver with a specific network interface.

Now I can write as below:

let (config, options) = trust_dns_resolver::system_conf::read_system_conf()?;

// but how can I set bind addr for config here. Since `set_bind_addr` is a method of `NameServerConfigGroup`, but `name_servers` in ResolverConfig is not public.

let provider = ...
let resolver = trust_dns_resolver::new_with_conn(config, options, provider)

I don't like copy the code how trust_dns_resolver::system_conf::read_system_conf() does and set bind addr there.

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And I think make a method named set_bind_addr for ResolverConfig will be a simple solution.

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https://github.com/hickory-dns/hickory-dns/blob/main/crates/resolver/src/config.rs#L827

[hainesc]

If that is acceptable, I can make a PR ASAP.

[hainesc]

Related issue:
#2087

[djc]

bind_addr is a public property of NameServerConfig so by itself that seems easy enough to change. I guess it might be okay to expose a groups_mut() accessor on ResolverConfig and a servers_mut() accessor on NameServerGroup?