[Windows] IPv6 is implemented (at least on some windows versions)

[geokala]

Hi,
I've been checking the windows_ping.dart while debugging a ping issue and noted that you have :
if (ipv6) throw UnimplementedError('IPv6 not implemented for windows');

For at least Server 2022 that's incorrect, tested using:

ping -w 2000 -i 255 -6 -n 5 ::1

Pinging ::1 with 32 bytes of data:
Reply from ::1: time<1ms
Reply from ::1: time<1ms
Reply from ::1: time<1ms
Reply from ::1: time<1ms
Reply from ::1: time<1ms

Ping statistics for ::1:
Packets: Sent = 5, Received = 5, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 0ms, Maximum = 0ms, Average = 0ms

This isn't something that is impacting me now, but I figured I'd report it as it appears to be functionality that could be provided.