[NI] Discriminate Nothing? result type from nullability constraints

Nullability constraints should not be chosen when proper
argument constraints for variables in contravariant position present.

^KT-32106 Fixed
^KT-33166 Fixed

compiler/testData/diagnostics/tests/inference/nestedCalls/preferArgumentToNullability.kt

@@ -0,0 +1,15 @@
+// !LANGUAGE: +NewInference
+// !DIAGNOSTICS: -UNUSED_PARAMETER
+
+open class Cls
+
+abstract class In<in I>
+class SubIn : In<Cls?>()
+
+inline fun <reified T : Cls> materialize(): T? = TODO()
+
+fun <D> transform(transformer: In<D>, data: D): Unit = TODO()
+
+fun test(subIn: SubIn) {
+    transform(subIn, materialize()) // D should be inferred to Cls?, not Nothing?
+}