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

compiler/testData/diagnostics/tests/smartCasts/variables/ifElseBlockInsideDoWhile.fir.kt

@@ -0,0 +1,15 @@
+public fun foo(xx: Any): Int {
+    var x = xx
+    do {
+        var y: Any
+        // After the check, smart cast should work
+        if (x is String) {
+            y = "xyz"
+        } else {
+            y = "abc"
+        }
+        // y!! in both branches
+        y.length
+    } while (!(x is String))
+    return x.<!UNRESOLVED_REFERENCE!>length<!>
+}