Run a nameserver for the {amnesia,tails}.boum.org sub-zones

… so our mirror admins can keep controlling it once boum.org’s NS has migrated to its new home.

Then:

• merge the 2 mirrors.git somehow
• adapt mirror team scripts if needed
• update mirror team doc
• add monitoring of this NS
• document on https://tails.boum.org/contribute/working_together/roles/sysadmins/ (#16254 (closed))

Related issues

• Blocks #13284
• Blocked by #15513 (closed)

Original created by @intrigeri on 16232 (Redmine)