JetDiagnosticsTest migrated to TestGenerator

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

compiler/testData/diagnostics/tests/regressions/kt399.kt

@@ -0,0 +1,11 @@
+// KT-399 Type argument inference not implemented for CALL_EXPRESSION
+
+fun <T> getSameTypeChecker(<!UNUSED_PARAMETER!>obj<!>: T) : Function1<Any,Boolean> {
+    return { (a : Any) -> a is T }
+}
+
+fun box() : String {
+    if(getSameTypeChecker<String>("lala")(10)) return "fail"
+    if(!getSameTypeChecker<String>("mama")("lala")) return "fail"
+    return "OK"
+}