feat: add debian12 scripts

- nftables_loopback_is_configured.sh 	-> 4.2.6
- nftables_established_connections.sh 	-> 4.2.7
- iptables_flushed_with_nftables.sh 	-> 4.2.3
- ufw_loopback_is_configured.sh 	-> 4.1.4
- ufw_outbound_connection.sh 		-> 4.1.5
- ufw_default_deny.sh 			-> 4.1.7
- ufw_rules_them_all.sh 		-> 4.1.6

tests/hardening/nftables_established_connections.sh

@@ -0,0 +1,16 @@
+# shellcheck shell=bash
+# run-shellcheck
+test_audit() {
+    describe Prepare test
+    apt install -y nftables
+
+    # not much to test here, unless working on a privileged container
+    describe Running on blank host
+    register_test retvalshouldbe 1
+    # shellcheck disable=2154
+    run blank "${CIS_CHECKS_DIR}/${script}.sh" --audit-all
+
+    describe clean test
+    apt remove -y nftables
+
+}