feat: add debian12 scripts

- iptables_loopback.sh 			-> 4.3.2.2
- iptables_rules_them_all.sh 		-> 4.3.2.4
- iptables_outbound_established.sh 	-> 4.3.2.3
- ip6tables_loopback.sh			-> 4.3.3.2
- ip6tables_outbound_established.sh	-> 4.3.3.3
- ip6tables_rules_them_all.sh		-> 4.3.3.4
- ip6tables_default_deny_policy.sh 	-> 4.3.3.1

tests/utils.sh

@@ -0,0 +1,26 @@
+tests_is_ipv6_enabled() {
+    CURRENT_IPV6_ENABLED=1
+    if sysctl net.ipv6 >/dev/null 2>&1; then
+        for iface in /proc/sys/net/ipv6/conf/*; do
+            ifname=$(basename "$iface")
+            if [ "$ifname" != "default" ] && [ "$ifname" != "all" ]; then
+                value=$(cat "$iface"/disable_ipv6)
+                # if only one interface has ipv6, this is enough to consider it enabled
+                if [ "$value" -eq 0 ]; then
+                    CURRENT_IPV6_ENABLED=0
+                    break
+                fi
+            fi
+        done
+    fi
+}
+
+tests_get_debian_major_version() {
+    DEB_MAJ_VER=""
+    if [ -e /etc/debian_version ]; then
+        DEB_MAJ_VER=$(cut -d '.' -f1 /etc/debian_version)
+    else
+        # shellcheck disable=2034
+        DEB_MAJ_VER=$(lsb_release -r | cut -f2 | cut -d '.' -f 1)
+    fi
+}