Rebase our patches on top of Icedove 38

Feature Branch: icedove:tails-secure_account_creation-38.6.0

Parent Task: #6154 (closed)

Related issues

• Has duplicate #9492 (closed)
• Blocks #6369 (closed)
• Blocked by #7064 (closed)

Original created by @intrigeri on 7746 (Redmine)