text: Title: DNS Resolver: Add `getaddrinfo` fallback
  Body: #### Problem Description
  
  Based on https://github.com/mitmproxy/mitmproxy/issues/7064, hickory's functionality to determine the OS name servers seems to have issues on both Linux and Windows. As much as I prefer hickory, we should have a fallback that uses `getaddrinfo`. This restores at least some basic functionality.
  
  Implementation-wise, this likely means we should change `DnsResolver.name_servers` to return an empty list if it's unable to determine servers. This way it's cached (whereas an exception is not).
  
  #### Steps to reproduce the behavior:
  
  1. Run mitmproxy in WireGuard mode on a setup where hickory is unable to determine nameservers.