[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/preferNothingToBound.kt

@@ -0,0 +1,3 @@
+fun <K> id(arg: K): K = arg
+
+val v = <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Nothing?")!>id(null)<!>