refactor: move httptransport w/ logging to netxlite (#411)

Part of https://github.com/ooni/probe/issues/1505

internal/engine/netx/dialer/dialer.go

@@ -25,6 +25,9 @@ type Resolver interface {
 type Logger interface {
 	// Debugf formats and emits a debug message.
 	Debugf(format string, v ...interface{})
+
+	// Debug emits a debug message.
+	Debug(msg string)
 }
 
 // Config contains the settings for New.