JetDiagnosticsTest migrated to TestGenerator

- test data files renamed from *.jet to *.kt

compiler/testData/diagnostics/tests/extensions/GenericIterator2.kt

@@ -0,0 +1,14 @@
+import java.util.Enumeration
+
+inline fun <T> java.util.Enumeration<T>.iterator() = object : Iterator<T> {
+  public override val hasNext: Boolean
+    get() = hasMoreElements()
+
+  public override fun next() = nextElement()
+}
+
+fun a(e : java.util.Enumeration<Int>) {
+    for (i in e) {
+        i : Int
+    }
+}