Introduce Tor network settings and other updates in TB9 onboarding

We should update users on the following changes:

• The Tor button is not at the toolbar anymore.

• Tor Network Settings were moved from the Tor button to about:preferences#tor https://trac.torproject.org/projects/tor/ticket/31286

• New Identity has a new icon at the toolbar and at the [≡] menu https://trac.torproject.org/projects/tor/ticket/27511