`disable_host_loopback` allows connections to localhost through 10.0.2.3

Hi,

I would like to fix this. It is also mentioned in !30 (merged). And we talked about it in slirp4net issue 93

Proposed solution is to restrict looback access through 10.0.2.3 to port 53 only. (To keep existing applications unaffected) And introduce disable_local_dns which additionally disables port 53 on 10.0.2.3.

I would like to include this in !30 (merged). Unless you would like separate merge request. Also I would like this to be released with 4.2.0, so it can be propagated to slirp4net and podman.

Do you have any suggestions or requirements to get this done ? And can I include it in !30 (merged)? (Ofc I would rename it to something like specific ip binding and more restrictive host loopback)