[NI] Continue resolution after unstable smart cast on receiver

The old inference cosideres candidates with unstable smartcast on
receiver unsuccessful, therefore another one may be selected.
KT-36264

compiler/testData/diagnostics/tests/smartCasts/varnotnull/unnecessaryWithMap.fir.kt

@@ -1,3 +1,5 @@
+// !WITH_NEW_INFERENCE
+
 fun create(): Map<String, String> = null!!
 
 operator fun <K, V> Map<K, V>.iterator(): Iterator<Map.Entry<K, V>> = null!!

compiler/testData/diagnostics/tests/smartCasts/varnotnull/unnecessaryWithMap.kt

@@ -1,3 +1,5 @@
+// !WITH_NEW_INFERENCE
+
 fun create(): Map<String, String> = null!!
 
 operator fun <K, V> Map<K, V>.iterator(): Iterator<Map.Entry<K, V>> = null!!
@@ -13,7 +15,7 @@ class MyClass {
         m = create()
         // See KT-7428
         for ((k, v) in <!SMARTCAST_IMPOSSIBLE!>m<!>)
-            res += (k.length + v.length)
+            res <!NI;OVERLOAD_RESOLUTION_AMBIGUITY!>+=<!> (<!NI;DEBUG_INFO_ELEMENT_WITH_ERROR_TYPE!>k<!>.<!NI;DEBUG_INFO_ELEMENT_WITH_ERROR_TYPE!>length<!> <!NI;DEBUG_INFO_ELEMENT_WITH_ERROR_TYPE!>+<!> <!NI;DEBUG_INFO_ELEMENT_WITH_ERROR_TYPE!>v<!>.<!NI;DEBUG_INFO_ELEMENT_WITH_ERROR_TYPE!>length<!>)
         return res
     }
 }