Upgrade to Tor Browser based on Firefox ESR60

Originally created by @intrigeri on #15023 (Redmine)

Relevant upstream tickets: https://trac.torproject.org/projects/tor/query?status=!closed&keywords=~ff60-esr&max=256

Foreseeable issues:

• See subtasks.
• Likely there will be a non-XUL (or system add-on) Tor Launcher to migrate to.
• Likely Torbutton will be installed in a different manner. XXX: reference needed
• sandboxing improvements require unprivileged user namespaces to be enabled + some AppArmor tweaks: is the risk/benefit worth it? this does not have to be solved as part of this ticket but it’s something to keep in mind and if not dealt with here, a follow-up ticket shall be created

Feature Branch: feature/15023-tor-browser-8, torbrowser-launcher:feature/15023-tor-browser-8

Subtasks

• #14555 (closed)
• #15530 (closed)
• #15531 (closed)
• #15701 (closed)
• #15702 (closed)
• #15703 (closed)
• #15704 (closed)
• #15705 (closed)
• #15707 (closed)
• #15708 (closed)
• #15716 (closed)
• #15717 (closed)
• #15719 (closed)
• #15773 (closed)
• #15777 (closed)

Related issues

• Related to #15092 (closed)
• Related to #12571
• Related to #15706 (closed)
• Blocks tails/accounting#15334
• Blocks #14962 (closed)
• Blocks #15720 (closed)
• Blocks #14771 (closed)
• Blocks #7759 (closed)
• Blocks #15725
• Blocks #15101 (closed)
• Blocks #11711 (closed)