DNS: Allow DOH and DOT servers to be added

Currently, when adding internal or primary DNS servers to Netbird, we only have the option to add “legacy” DNS, e. g. udp/53.

It would be nice if we could add more modern and privacy-focussed options like DNS over HTTPS or DNS over TCP/Quic.

This would open up secure DNS options like NextDNS and Cloudflare Gateway to filter malicious domains, ads, and more.