[FE] Always infer upper types to intersection types in K2...

...and always use old algorithm for K1

^KT-51221

compiler/testData/diagnostics/testsWithStdLib/inference/annotationsForResolve/exactAnnotation.fir.kt

@@ -7,5 +7,5 @@ fun test1(l: List<Number>) {
 
     val i: Int = l.firstTyped()
 
-    val s: String = <!INITIALIZER_TYPE_MISMATCH, NEW_INFERENCE_ERROR!>l.firstTyped()<!>
+    val s: String = l.<!INFERRED_TYPE_VARIABLE_INTO_EMPTY_INTERSECTION!>firstTyped<!>()
 }