retire or replace scaleway boxes (scw-arm-*)

the boxes we have at scaleway (scw-arm-ams-01 and scw-arm-par-01) are "old" according to scaleway. this leads to various problems, documented in their ticket tracker:

• #WJVJ-9718-KIPG - machines do not reboot unattended
• #GHYX-4885-QWLA - kernel not used

Their newer platform allows us to run our own kernels, and also handles reboots better. Right now scq-arm-ams-01 is down because I can't figure out how to reboot it properly, for example.

This would require reinstalling the machines and setting them up as build boxes again.

1. announced the change (service stopped in jenkins in early April, announce sent to tor-project on 2021-04-21)
2. remove host from nagios
3. stop VM (N/A, need to wipe the machine first)
4. after delay, retire host from parent, backups, and puppet
5. remove from LDAP
6. power-grep to remove the IP
7. remove from tor-passwords
8. remove from DNSwl (N/A)
9. remove from wiki, inventory
10. wipe the machine at scaleway
11. remove from reverse DNS