Migrate away from dnslib

[nhairs]

As of 2024-06-08 dnslib is in maintenance mode.

Whilst I did look at modernising it / bringing it back into support, it looks like the author does not have the time to continue under the original project. I personally do not have the time to fork and maintain a new project.

It does look like there is another effort to fork the project with Alviner/dnslib3, however given it is new and doesn't have a lot of community around it I'm not sure that relying on it is the best idea.

Thus I believe it would be prudent to migrate to a new DNS library that can handle reading from / writing to wire format. I'll note that changing the underlying DNS library will affect all the "raw server" related things, but should leave our high level stuff alone.

Since I started NServer it looks like rthalley/dnspython has greatly matured and may be a good alternative.