Support nftables

**Is your feature request related to a problem? Please describe.**
https://github.com/mysteriumnetwork/node/issues/6134#issuecomment-3221931641

**Describe the solution you'd like**
Port the current iptables auto configuration to nftables.

**Describe alternatives you've considered**
Provide clear nftables rules in docs to follow.

**Additional context**
None.
