Display Tor Launcher to all users by default

Originally created by @sajolida on #17330 (Redmine)

See https://tails.boum.org/blueprint/network_connection/#index1h2, iteration 1.

This implies (see blueprint for details):

• we have to not restart Tor anymore when exiting the Unsafe Browser, otherwise this breaks Tor Launcher.
• Worsens issues: F (temporarily and for 1st time users affected by issue F, until they understand that the new behaviour behaves by default, all of the time, in they way they had to opt-in for previously). → Add a temporary note about the change in Tails Greeter.