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

compiler/testData/diagnostics/tests/smartCasts/varnotnull/assignNestedWhile.fir.kt

@@ -0,0 +1,28 @@
+class Bar {
+    fun next(): Bar? {
+        if (2 == 4)
+            return this
+        else
+            return null
+    }
+}
+
+fun foo(): Bar {
+    var x: Bar? = Bar()
+    var y: Bar?
+    y = Bar()
+    while (x != null) {
+        // Here call is unsafe because of inner loop
+        y.next()
+        while (y != null) {
+            if (x == y)
+                // x is not null because of outer while
+                return x
+            // y is not null because of inner while
+            y = y.next()
+        }
+        // x is not null because of outer while
+        x = x.next()
+    }
+    return Bar()
+}