[IC] Add tests for sealed classes (KT-45474)

jps/jps-plugin/testData/incremental/pureKotlin/sealedClassesWhenExpression/Usage.kt

@@ -0,0 +1,12 @@
+package test
+
+//sealed interface Base
+
+class Usage {
+
+    fun doSmth(x: Base) =
+        when (x) {
+            is A -> "A"
+            is B -> "B"
+        }
+}