Revert "daemon: Forbid IPv6 BPF masquerading with the host firewall"

[qmonnet]

This reverts commit 934e1f2.

Since commit 9c1031e ("bpf: fix missing ipv6 ct entry for snated traffic"), IPv6 BPF masquerading and the host firewall are compatible in the datapath. Let's allow them to be used together, and use the combination in tests.

CC: @oblazek
Supersedes: #26323

Allow the Host Firewall and IPv6 BPF masquerading to be used together.

[qmonnet]

/test

[julianwiedmann]

Since commit 9c1031e ("bpf: fix missing ipv6 ct entry for snated traffic"), IPv6 BPF masquerading and the host firewall are compatible in the datapath. Let's allow them to be used together, and use the combination in tests.

From what I remember in #23165, we were concerned about HostFW and IPv6 BPF Masq interacting.

But turns out the problematic interaction was for HostFW and iptables Masquerading (ie. when BPF Masq is disabled). This is what #28813 fixed. So afaik there were no actual problems for HostFW and IPv6 BPF Masq, and 👍 on allowing this combo.

We could even backport, but at this point I don't see the need.