JetDiagnosticsTest migrated to TestGenerator

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

compiler/testData/diagnostics/tests/controlFlowAnalysis/kt510.kt

@@ -0,0 +1,18 @@
+//KT-510 `this.` allows initialization without backing field
+
+package kt510
+
+public open class Identifier1() {
+    var field : Boolean
+    {
+        field = false; // error
+    }
+}
+
+
+public open class Identifier2() {
+    var field : Boolean
+    {
+        this.field = false;
+    }
+}