[FIR] Add PLATFORM_CLASS_MAPPED_TO_KOTLIN

compiler/fir/analysis-tests/testData/resolveWithStdlib/intellij/IntersectionWithJavaString.kt

@@ -1,7 +1,8 @@
 // FULL_JDK
 // ISSUE: KT-48113
+// WITH_EXTENDED_CHECKERS
 
 fun collapse(path: String) {
-    val result = (path as java.lang.String).replace("123", "456")
+    val result = (path as <!PLATFORM_CLASS_MAPPED_TO_KOTLIN!>java.lang.String<!>).replace("123", "456")
     if (result !== path) {}
 }