PSI Pattern Matching: Add equivalence tests for JetPsiUnifier

idea/testData/unifier/equivalence/controlStructures/continue.kt

@@ -0,0 +1,16 @@
+fun foo(a: Int) {
+    @A
+    while (true) {
+        @B
+        while (true) {
+            if (a > 0) <selection>continue@A</selection>
+            if (a < 0) continue@B
+        }
+
+        @B
+        while (true) {
+            if (a > 0) continue@A
+            if (a < 0) continue@B
+        }
+    }
+}