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

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

@@ -0,0 +1,12 @@
+fun x(): Boolean { return true }
+
+public fun foo(p: String?): Int {
+    // KT-6284
+    while(true) {
+        p!!.length
+        if (x()) break
+    }
+    // while (true) loop body is executed at least once
+    // so p is not null here
+    return p.length
+}