[FIR] Prefer the non-smartcasted receiver in resolution if it's visible

Previously, we would ignore the candidate with the non-smartcasted
receiver if they have the same symbol.
Now we prefer them when they're visible or when the smart cast changes
the nullability.

compiler/testData/ir/irText/classes/smartCastInValInitialization.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 class RootBus: MessageBusImpl()
 
 open class MessageBusImpl {