[release-1.22] Support dual-stack in klipper-lb

[manuelbuil]

• Backport of Support dual-stack in klipper-lb #4021 on branch release-1.22

Is your feature request related to a problem? Please describe.

Dual-stack services in load-balanced mode are not working because klipper-lb does not support it:

+ iptables -t nat -I PREROUTING '!' -s 2001:cafe:42:1::def/32 -p TCP --dport 8080 -j DNAT --to 2001:cafe:42:1::def:8080
iptables v1.6.2: Port `cafe:42:1::def:8080' not valid

Describe the solution you'd like

klipper-lb is able to apply an ipv6 config

Additional context

#1405

[rancher-max]

Validated the config at /proc/sys/net/ipv6/conf/all/forwarding inside the pods matches the host (both set to 1) using v1.22.2-rc1+k3s2 and the current validated ipv6 functionality continues to work.

[manuelbuil]

There is a PR missing to properly test this :) ==> #4114

[ShylajaDevadiga]

Validated in the new rc v1.22.3-rc3+k3s1 #4021