Remove dependencies on data flow aware expression type in BindingContext

`BindingContext.getType`'s behaviour on argument expression has been different for OI and NI for some time.
New inference used to rewrite argument's type after smartcast, which led to missing subsequent smartcasts in some cases.
This commit makes retrieval of smartcasted argument type explicit.

nj2k/testData/newJ2k/postProcessing/IfToElvis.kt

@@ -1,5 +1,5 @@
 internal class C {
-    fun foo(s: String?): String? {
+    fun foo(s: String?): String {
         return s ?: ""
     }
 }