Support IPv6-only server and Colocation

[sinuscosinustan]

Hetzner offers IPv6-Only for Bare-Metal systems for since Nov. 2021. The current server_ip field is empty and the server_ipv6_net is filled instead. The query for the server can't be made via the Legacy-IP address anymore, but via the server id.

E.g. Colocation does not support server reset.

Server:
$ hetznerctl show 123
Number:        123
Main IP:       None
Name:          footlong-meatless-teriyaki
Product:       RX170
Data center:   FSN1-DC17
Traffic:       unlimited
Status:        ready
Cancelled:     False
Paid until:    1970-01-01 00:00:00
Traceback (most recent call last): [TRUNCATED]
hetzner.RobotError: 404 - server not found (404)

Colocation:
$ hetznerctl show 122 
Number:        122
Main IP:       None
Name:          filet-o-fish
Product:       Colocation Rack Basic
Data center:   FSN1-DC2-LOC9999-9999
Traffic:       10 TB
Status:        ready
Cancelled:     False
Paid until:    1970-01-01 00:00:00
hetzner.RobotError: 404 - server not found (404)