testing: Add scenarios that use a CA with two intermediate CA certificates

Mainly to test TKM's ability for handling multiple CAs and that the
received intermediate CA certificates are passed in the right order.
But also added a regular scenario where two intermediate CA certificates
are sent by one of the clients.

testing/tests/tkm/multi-level-ca/hosts/moon/etc/strongswan.conf.in

@@ -0,0 +1,21 @@
+# /etc/strongswan.conf - strongSwan configuration file
+
+charon-tkm {
+  dh_mapping {
+    15 = 1
+    16 = 2
+  }
+  ca_mapping {
+    strongswan_ca {
+      id = 1
+      fingerprint = CA_SPK_HEX
+    }
+    levels_ca {
+      id = 2
+      fingerprint = LEVELS_SPK_HEX
+    }
+  }
+  start-scripts {
+    swanctl = /usr/local/sbin/swanctl --load-all --noprompt
+  }
+}