Tor Connection Assistant

This includes:

• a rewrite of Tor Launcher, called Tor Connection Assistant: closes #17215 (closed)
• always starting Tor Launcher (previously tracked on !326 (closed)): closes #17330 (closed), #16993 (closed), #11535 (closed)

Also closes #9051 (closed), #8825 (closed), #6898 (closed), #18007 (closed)