Safe Delete: Move test classes and test data to refactoring directory

idea/testData/refactoring/safeDelete/deleteFunction/javaFunctionWithKotlin/mixedHierarchy2.kt

@@ -0,0 +1,11 @@
+interface B: A {
+    public override fun foo() {
+        throw UnsupportedOperationException()
+    }
+}
+
+class D: C() {
+    public override fun foo() {
+        throw UnsupportedOperationException()
+    }
+}