testing: Add ikev2/compress-nat scenario

testing/tests/ikev2/compress-nat/hosts/alice/etc/strongswan.conf

@@ -0,0 +1,5 @@
+# /etc/strongswan.conf - strongSwan configuration file
+
+charon {
+  load = curl aes des sha1 sha2 md5 pem pkcs1 gmp random nonce x509 revocation hmac xcbc stroke kernel-netlink socket-default updown
+}