Reflect Kotlin's declaration-site variance in Java signatures

compiler/testData/writeSignature/declarationSiteVariance/OutOfInInOutPosition.kt

@@ -0,0 +1,10 @@
+class In<in T>
+class Out<out T>
+class X
+
+fun f(): Out<In<X>> = throw Exception()
+
+// method: namespace::f
+// jvm signature:     ()LOut;
+// generic signature: ()LOut<LIn<-LX;>;>;
+// kotlin signature:  ()LOut<LIn<LX;>;>;