cleanup: netx does not use netxlite legacy names (#801)

This diff refactors netx and netxlite to ensure we're not using
netxlite legacy names inside of netx.

To this end, we're cheating a bit. We're exposing a new factory to
get an unwrapped stdlib resolver rather than defining a legacy name
to export the private name of the same factory.

This is actually a fine place to stop, for now, the next and
netxlite refactoring at https://github.com/ooni/probe/issues/2121.

internal/measurex/resolver.go

@@ -28,7 +28,7 @@ func WrapResolver(begin time.Time, db WritableDB, r model.Resolver) model.Resolv
 // NewResolverSystem creates a system resolver and then wraps
 // it using the WrapResolver function.
 func (mx *Measurer) NewResolverSystem(db WritableDB, logger model.Logger) model.Resolver {
-	return mx.WrapResolver(db, netxlite.NewResolverStdlib(logger))
+	return mx.WrapResolver(db, netxlite.NewStdlibResolver(logger))
 }
 
 // NewResolverUDP is a convenience factory for creating a Resolver

internal/measurex/tracing.go

@@ -54,7 +54,7 @@ func NewTracingHTTPTransport(logger model.Logger, begin time.Time, db WritableDB
 func NewTracingHTTPTransportWithDefaultSettings(
 	begin time.Time, logger model.Logger, db WritableDB) *HTTPTransportDB {
 	return NewTracingHTTPTransport(logger, begin, db,
-		netxlite.NewResolverStdlib(logger),
+		netxlite.NewStdlibResolver(logger),
 		netxlite.NewDialerWithoutResolver(logger),
 		netxlite.NewTLSHandshakerStdlib(logger),
 		DefaultHTTPMaxBodySnapshotSize)