JetDiagnosticsTest migrated to TestGenerator

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

compiler/testData/diagnostics/tests/annotations/kt1860-negative.kt

@@ -0,0 +1,9 @@
+fun foo(<!UNRESOLVED_REFERENCE!>varargs<!> <!UNUSED_PARAMETER!>f<!> : Int) {}
+
+var bar : Int = 1
+  set(<!UNRESOLVED_REFERENCE!>varargs<!> v) {}
+
+val x : (Int) -> Int = {([<!UNRESOLVED_REFERENCE!>varargs<!>] x : Int) -> x}
+
+class Hello(<!UNRESOLVED_REFERENCE!>varargs<!> args: Any) {
+}