* cleanup: remove UnderlyingNetworkLibrary and TProxy
While there, replace mixture of mocking and real connections inside
quicping with pure mocking of network connections.
Closes https://github.com/ooni/probe/issues/2224
* cleanup: we don't need a SimpleResolver now
This type was only used by UnderlyingNetworkLibrary and all the
rest of the code uses Resolver. So, let's avoid complexity by zapping
the SimpleResolver type and merging it inside Resolver.
This diff modifies the system resolver to use a getaddrinf transport.
Obviously the transport is a fake, but its existence will allow us
to observe DNS events more naturally.
A lookup using the system resolver would be a ANY lookup that will
contain all the resolved IP addresses into the same response.
This change was also part of websteps-illustrated, albeit the way in
which I did it there was less clean than what we have here.
Ref issue: https://github.com/ooni/probe/issues/2096
