add support for conntrack ctstate rules in iptables

### Description

Hi there! Please add support for filter rules in `stack.IPTables` that semantically equal to the following iptable rule:

```
-A FORWARD -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT
```

or nftables match:

```
ct state { established, related }
```

### Is this feature related to a specific bug?

_No response_

### Do you have a specific solution in mind?

_No response_