JS: Add test case for false flow through IIFEs

We generate local flow steps into and out of IIFEs, but these come jump steps automatically, resulting in FPs.

javascript/ql/test/library-tests/TripleDot/iife.js

@@ -0,0 +1,43 @@
+function f1() {
+    function inner(x) {
+        return (function(p) {
+            return p; // argument to return
+        })(x);
+    }
+    sink(inner(source("f1.1"))); // $ hasValueFlow=f1.1 SPURIOUS: hasValueFlow=f1.2
+    sink(inner(source("f1.2"))); // $ hasValueFlow=f1.2 SPURIOUS: hasValueFlow=f1.1
+}
+
+function f2() {
+    function inner(x) {
+        let y;
+        (function(p) {
+            y = p; // parameter to captured variable
+        })(x);
+        return y;
+    }
+    sink(inner(source("f2.1"))); // $ hasValueFlow=f2.1 SPURIOUS: hasValueFlow=f2.2
+    sink(inner(source("f2.2"))); // $ hasValueFlow=f2.2 SPURIOUS: hasValueFlow=f2.1
+}
+
+function f3() {
+    function inner(x) {
+        return (function() {
+            return x; // captured variable to return
+        })();
+    }
+    sink(inner(source("f3.1"))); // $ hasValueFlow=f3.1 SPURIOUS: hasValueFlow=f3.2
+    sink(inner(source("f3.2"))); // $ hasValueFlow=f3.2 SPURIOUS: hasValueFlow=f3.1
+}
+
+function f4() {
+    function inner(x) {
+        let y;
+        (function() {
+            y = x; // captured variable to captured variable
+        })();
+        return y;
+    }
+    sink(inner(source("f4.1"))); // $ hasValueFlow=f4.1
+    sink(inner(source("f4.2"))); // $ hasValueFlow=f4.2
+}