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

compiler/testData/diagnostics/tests/smartCasts/safecalls/receiverAndChain.fir.kt

@@ -0,0 +1,8 @@
+fun foo(x: String): String? = x
+
+fun calc(x: String?): Int {
+    // Smart cast because of x!! in receiver
+    foo(x!!)?.subSequence(0, x.length)?.length
+    // Smart cast because of x!! in receiver
+    return x.length
+}