Move unittest YAML files into their own directory, pending more python unit tests in a followup commit

unittest/yaml/error-subinterface3.yaml

@@ -0,0 +1,24 @@
+test:
+  description: "The length of the LCP name is too long"
+  errors:
+    expected:
+    - "sub-interface .* has LCP with too long name .*"
+    count: 2
+---
+interfaces:
+  GigabitEthernet1/0/0:
+    lcp: "e23456789012"
+    sub-interfaces:
+      100:
+        description: "VLAN 100"
+  GigabitEthernet1/0/1:
+    lcp: "e2345678"
+    sub-interfaces:
+      100:
+        description: "VLAN 100"
+      101:
+        description: "QinQ 101"
+        encapsulation:
+          dot1q: 100
+          inner-dot1q: 100
+