Merge #19638: Replace hidden service with onion service

1e72b68ab3 Replace `hidden service` with `onion service` (Riccardo Masutti)

Pull request description:

  For a couple of years, Tor has made the term `hidden service` obsolete, in favor of `onion service`: [Tor Project | Onion Services](https://community.torproject.org/onion-services/)

  This PR updates all the references.

ACKs for top commit:
  laanwj:
    Code review ACK 1e72b68ab3
  hebasto:
    ACK 1e72b68ab3, tested on Linux Mint 20 (x86_64).

Tree-SHA512: 6a29e828e1c5e1ec934b5666f67326dbd84d77c8b2641f6740abac6d3d5923b7729763b9ff2230390b0bb23359a5f3731ccd9a30011ca69004f7c820aed17262

src/qt/forms/optionsdialog.ui

@@ -459,10 +459,10 @@
        <item>
         <widget class="QCheckBox" name="connectSocksTor">
          <property name="toolTip">
-          <string>Connect to the Bitcoin network through a separate SOCKS5 proxy for Tor hidden services.</string>
+          <string>Connect to the Bitcoin network through a separate SOCKS5 proxy for Tor onion services.</string>
          </property>
          <property name="text">
-          <string>Use separate SOCKS&amp;5 proxy to reach peers via Tor hidden services:</string>
+          <string>Use separate SOCKS&amp;5 proxy to reach peers via Tor onion services:</string>
          </property>
         </widget>
        </item>