T160: NAT64 add match firewall mark feature

Match mark allows to use firewall marks of packet to use
a specific pool

Example of instance config /run/jool/instance-100.json
```
  ...
  "pool4": [
    {
      "protocol": "TCP",
      "prefix": "192.0.2.10",
      "port range": "1-65535",
      "mark": 23
    },
   ...
```

1 files changed, 7 insertions, 0 deletions

diff --git a/src/conf_mode/nat64.py b/src/conf_mode/nat64.py
index a8b90fb11..6026c61d0 100755
--- a/src/conf_mode/nat64.py
+++ b/src/conf_mode/nat64.py
@@ -148,6 +148,11 @@ def generate(nat64) -> None:
 
             if dict_search("translation.pool", instance):
                 pool4 = []
+                # mark
+                mark = ''
+                if dict_search("match.mark", instance):
+                    mark = instance["match"]["mark"]
+
                 for pool in instance["translation"]["pool"].values():
                     if "disable" in pool:
                         continue
@@ -159,6 +164,8 @@ def generate(nat64) -> None:
                             "prefix": pool["address"],
                             "port range": pool["port"],
                         }
+                        if mark:
+                            obj["mark"] = int(mark)
                         if "description" in pool:
                             obj["comment"] = pool["description"]