[JS IR] Optimize JS AST for closures

^KT-58891 Fixed

js/js.translator/testData/box/jsAstOptimizations/deadCodeElimination.kt

@@ -0,0 +1,23 @@
+// IGNORE_BACKEND_K2: JS_IR
+// FIR works fine, however it generates another names for the temporary variables, therefore ignore it
+
+fun demo(f: () -> String) = f()
+
+// EXPECT_GENERATED_JS: function=test$lambda expect=deadCodeEliminationTestLambda.js
+fun test(x: String?): String {
+    val r = demo {
+        val z = x ?: run {
+            return@demo "OK"
+        }
+        "Fail 1: $z"
+    }
+    return r
+}
+
+fun box(): String {
+    val r = test(null)
+    if (r != "OK") {
+        return "Fail test, got $r"
+    }
+    return "OK"
+}