LibJS: Extend class 'extends' RHS expression parsing

Instead of only parsing a primary expression, we should also allow
member expressions, call expressions, and tagged template literals (and
optional chains, which we don't have yet).
In the spec, all of this is covered by `LeftHandSideExpression`
(https://tc39.es/ecma262/#prod-LeftHandSideExpression).

Userland/Libraries/LibJS/Tests/classes/class-inheritance.js

@@ -132,6 +132,24 @@ test("super constructor call from child class with argument", () => {
     expect(c.x).toBe(10);
 });
 
+test("advanced 'extends' RHS", () => {
+    const foo = {
+        bar() {
+            return {
+                baz() {
+                    return function () {
+                        return function () {
+                            return { quux: Number };
+                        };
+                    };
+                },
+            };
+        },
+    };
+    class Foo extends foo.bar()["baz"]()`qux`().quux {}
+    expect(new Foo()).toBeInstanceOf(Number);
+});
+
 test("issue #7045, super constructor call from child class in catch {}", () => {
     class Parent {
         constructor(x) {