Add test case for IIFE const declaration bug fix

Co-authored-by: kdy1 <29931815+kdy1@users.noreply.github.com>

Author: Copilot

crates/swc_ecma_minifier/tests/fixture/iife_const_bug/config.json

@@ -0,0 +1,6 @@
+{
+  "unused": true,
+  "negate_iife": true,
+  "collapse_vars": true,
+  "evaluate": true
+}

crates/swc_ecma_minifier/tests/fixture/iife_const_bug/input.js

@@ -0,0 +1,4 @@
+(function () {
+    const obj = { value: 42 };
+    console.log(obj === null || obj === void 0 ? void 0 : obj.value)
+})()

crates/swc_ecma_minifier/tests/fixture/iife_const_bug/output.js

@@ -0,0 +1,6 @@
+!function() {
+    const obj = {
+        value: 42
+    };
+    console.log(null == obj ? void 0 : obj.value);
+}();