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

compiler/testData/diagnostics/tests/smartCasts/inference/smartCastOnReceiver.fir.kt

@@ -0,0 +1,13 @@
+interface A
+interface B
+
+class Test {
+    fun test(a: A?, b: B, list: MutableList<Pair<A, B>>) {
+        if (a != null) {
+            list.add(a to b)
+        }
+    }
+}
+
+class Pair<out A, out B>(val first: A, val second: B)
+infix fun <A, B> A.to(that: B) = Pair(this, that)