JetDiagnosticsTest migrated to TestGenerator

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

compiler/testData/diagnostics/tests/override/ComplexValRedeclaration.kt

@@ -0,0 +1,9 @@
+package override.generics
+
+abstract class MyAbstractClass<T> {
+    abstract val pr : T
+}
+
+abstract class MyLegalAbstractClass2<T>(t : T) : MyAbstractClass<Int>() {
+    <!CONFLICTING_OVERLOADS!>val <R> pr : T<!> = t
+}