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

compiler/testData/diagnostics/tests/smartCasts/loops/whenInsideWhileTrue.fir.kt

@@ -0,0 +1,12 @@
+public fun foo(x: String?): Int {
+    loop@ while (true) {
+        when (x) {
+            null -> break@loop
+            "abc" -> return 0
+            "xyz" -> return 1
+            else -> x.length
+        }         
+    }
+    // x is null because of the break
+    return x.<!INAPPLICABLE_CANDIDATE!>length<!>
+}