Failover for lizard

Originally created by @intrigeri on #6185 (Redmine)

Team: bertagaz, intrigeri

Blueprint: https://tails.boum.org/blueprint/lizard_failover/

Subtasks

• tails/sysadmin#6186
• tails/tails#6190
• tails/tails#6191
• tails/tails#6249
• tails/sysadmin#6250
• #10243 (closed)
• tails/sysadmin#10244