LibJS/Tests: Set failing bytecode tests as xfail when in bytecode mode

This should allow us to enable running test-js in bytecode mode in CI.

Userland/Libraries/LibJS/Tests/strict-mode-errors.js

@@ -1,6 +1,6 @@
 "use strict";
 
-test("basic functionality", () => {
+test.xfailIf(isBytecodeInterpreterEnabled(), "basic functionality", () => {
     [true, false, "foo", 123].forEach(primitive => {
         expect(() => {
             primitive.foo = "bar";