LibJS: Implement Object.hasOwn() :^)

This is currently a TC39 Stage 2 proposal, but let's go for it!

https://github.com/tc39/proposal-accessible-object-hasownproperty

I wrote the C++, @linusg found bugs and wrote the test.

Userland/Libraries/LibJS/Tests/builtins/Object/Object.hasOwn.js

@@ -0,0 +1,35 @@
+describe("basic functionality", () => {
+    test("length", () => {
+        expect(Object.hasOwn).toHaveLength(2);
+    });
+
+    test("returns true for existent own property", () => {
+        const o = { foo: "bar" };
+        expect(Object.hasOwn(o, "foo")).toBeTrue();
+    });
+
+    test("returns false for non-existent own property", () => {
+        const o = {};
+        expect(Object.hasOwn(o, "foo")).toBeFalse();
+    });
+
+    test("returns false for existent prototype chain property", () => {
+        const o = {};
+        Object.prototype.foo = "bar";
+        expect(Object.hasOwn(o, "foo")).toBeFalse();
+    });
+});
+
+describe("errors", () => {
+    test("null argument", () => {
+        expect(() => {
+            Object.hasOwn(null);
+        }).toThrowWithMessage(TypeError, "ToObject on null or undefined");
+    });
+
+    test("undefined argument", () => {
+        expect(() => {
+            Object.hasOwn(undefined);
+        }).toThrowWithMessage(TypeError, "ToObject on null or undefined");
+    });
+});