[FIR-TEST] Add new testdata generated after changes in previous commit

compiler/testData/diagnostics/tests/when/NonExhaustiveWarningForSealedClass.fir.kt

@@ -0,0 +1,16 @@
+sealed class S
+
+object First : S()
+
+class Derived(val s: String) : S()
+
+object Last : S()
+
+fun use(s: String) = s
+
+fun foo(s: S) {
+    when (s) {
+        First -> {}
+        is Derived -> use(s.s)
+    }
+}