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

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