JetDiagnosticsTest migrated to TestGenerator

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

compiler/testData/diagnostics/tests/controlFlowAnalysis/kt607.kt

@@ -0,0 +1,18 @@
+//KT-607 Val reassignment is not marked as an error
+
+package kt607
+
+fun foo(a: A) {
+    val o = object {
+        val y : Int
+           get() = 42
+    }
+
+    <!VAL_REASSIGNMENT!>a.z<!> = 23
+    <!VAL_REASSIGNMENT!>o.y<!> = 11   //Should be an error here
+}
+
+class A() {
+    val z : Int
+    get() = 3
+}