Replace hidden service with onion service

For a couple of years, Tor documentation has made
the term hidden service obsolete, in favor of onion
service.

This PR updates all the references in the code base.

src/torcontrol.cpp

@@ -405,7 +405,7 @@ static bool WriteBinaryFile(const fs::path &filename, const std::string &data)
 /****** Bitcoin specific TorController implementation ********/
 
 /** Controller that connects to Tor control socket, authenticate, then create
- * and maintain an ephemeral hidden service.
+ * and maintain an ephemeral onion service.
  */
 class TorController
 {
@@ -534,7 +534,7 @@ void TorController::auth_cb(TorControlConnection& _conn, const TorControlReply&
         // Finally - now create the service
         if (private_key.empty()) // No private key, generate one
             private_key = "NEW:RSA1024"; // Explicitly request RSA1024 - see issue #9214
-        // Request hidden service, redirect port.
+        // Request onion service, redirect port.
         // Note that the 'virtual' port is always the default port to avoid decloaking nodes using other ports.
         _conn.Command(strprintf("ADD_ONION %s Port=%i,127.0.0.1:%i", private_key, Params().GetDefaultPort(), GetListenPort()),
             std::bind(&TorController::add_onion_cb, this, std::placeholders::_1, std::placeholders::_2));