pkg/networks/usernet: use domain.tld zones

[julego]

The usernet client stores dns records in tld zones, and as such the default host.lima.internal record breaks resolving .internal domains that may exist on the host network (e.g. compute.internal, dev.internal, etc).

This is a proposal to store dns records in domain.tld zones to be able to use such domains.

It may close #3161 also.

[AkihiroSuda]

CI failing

ping: lima-net-user-v2-1.internal: Name or service not known

https://github.com/lima-vm/lima/actions/runs/23485110542/job/69213743913?pr=4772

[julego]

I just checked the test, it failed because the dns server implemented in gvisor-tap-vsock doesn't seem to handle domain.tld zones so well.

With domain.tld zones, sublevel records such as project.dev.tld are well resolved by gvisor-tap-vsock (what I was testing on my dev env) but root records like dev.tld are not (whether the tld is ".internal" or not). Hence the test failing with "lima-net-user-v2-1.internal".

I'll have a look at this but gvisor-tap-vsock will probably need a patch too, I don't think there's a direct fix in lima.