testing: Add libipsec scenarios that exchange raw ESP packets

testing/tests/libipsec/net2net-cert-ip6-in-ip4/hosts/sun/etc/strongswan.conf

@@ -0,0 +1,10 @@
+# /etc/strongswan.conf - strongSwan configuration file
+
+swanctl {
+  load = pem pkcs1 x509 revocation constraints pubkey openssl random
+}
+
+charon-systemd {
+  load = random nonce pem pkcs1 x509 openssl curl revocation vici kernel-libipsec kernel-netlink socket-default updown
+  multiple_authentication = no
+}