FIR LC: use optimal type mapping mode for return type

compiler/testData/asJava/lightClasses/nullabilityAnnotations/PlatformTypes.kt

@@ -6,4 +6,6 @@ class PlatformTypes {
     fun simplyPlatform() = Collections.singletonList("")[0]
     fun bothNullable() = Collections.emptyList<String>() ?: null
     fun bothNotNull() = Collections.emptyList<String>()!!
-}
+}
+
+// FIR_COMPARISON

compiler/testData/asJava/ultraLightClasses/wildcardOptimization.kt

@@ -51,3 +51,5 @@ class Container {
 
     fun <Q : Final> typeParameter(x: Out<Q>, y: In<Q>) {}
 }
+
+// FIR_COMPARISON