LibJS: Implement non-ECMA-402 String.prototype.toLocale{Lower,Upper}Case

In implementations without ECMA-402, these methods are to behave like
their non-locale equivalents.

Userland/Libraries/LibJS/Tests/builtins/String/String.prototype.toLocaleLowerCase.js

@@ -0,0 +1,28 @@
+test("basic functionality", () => {
+    expect(String.prototype.toLocaleLowerCase).toHaveLength(0);
+
+    expect("ω".toLocaleLowerCase()).toBe("ω");
+    expect("Ω".toLocaleLowerCase()).toBe("ω");
+    expect("😀".toLocaleLowerCase()).toBe("😀");
+
+    expect("foo".toLocaleLowerCase()).toBe("foo");
+    expect("Foo".toLocaleLowerCase()).toBe("foo");
+    expect("FOO".toLocaleLowerCase()).toBe("foo");
+
+    expect(("b" + "a" + +"a" + "a").toLocaleLowerCase()).toBe("banana");
+});
+
+test("special case folding", () => {
+    expect("\u00DF".toLocaleLowerCase()).toBe("\u00DF");
+    expect("\u0130".toLocaleLowerCase()).toBe("\u0069\u0307");
+    expect("\uFB00".toLocaleLowerCase()).toBe("\uFB00");
+    expect("\uFB01".toLocaleLowerCase()).toBe("\uFB01");
+    expect("\uFB02".toLocaleLowerCase()).toBe("\uFB02");
+    expect("\uFB03".toLocaleLowerCase()).toBe("\uFB03");
+    expect("\uFB04".toLocaleLowerCase()).toBe("\uFB04");
+    expect("\uFB05".toLocaleLowerCase()).toBe("\uFB05");
+    expect("\uFB06".toLocaleLowerCase()).toBe("\uFB06");
+    expect("\u1FB7".toLocaleLowerCase()).toBe("\u1FB7");
+    expect("\u1FC7".toLocaleLowerCase()).toBe("\u1FC7");
+    expect("\u1FF7".toLocaleLowerCase()).toBe("\u1FF7");
+});

Userland/Libraries/LibJS/Tests/builtins/String/String.prototype.toLocaleUpperCase.js

@@ -0,0 +1,30 @@
+test("basic functionality", () => {
+    expect(String.prototype.toLocaleUpperCase).toHaveLength(0);
+
+    expect("ω".toLocaleUpperCase()).toBe("Ω");
+    expect("Ω".toLocaleUpperCase()).toBe("Ω");
+    expect("😀".toLocaleUpperCase()).toBe("😀");
+
+    expect("foo".toLocaleUpperCase()).toBe("FOO");
+    expect("Foo".toLocaleUpperCase()).toBe("FOO");
+    expect("FOO".toLocaleUpperCase()).toBe("FOO");
+
+    expect(("b" + "a" + +"n" + "a").toLocaleUpperCase()).toBe("BANANA");
+});
+
+test("special case folding", () => {
+    expect("\u00DF".toLocaleUpperCase()).toBe("\u0053\u0053");
+    expect("\u0130".toLocaleUpperCase()).toBe("\u0130");
+    expect("\uFB00".toLocaleUpperCase()).toBe("\u0046\u0046");
+    expect("\uFB01".toLocaleUpperCase()).toBe("\u0046\u0049");
+    expect("\uFB02".toLocaleUpperCase()).toBe("\u0046\u004C");
+    expect("\uFB03".toLocaleUpperCase()).toBe("\u0046\u0046\u0049");
+    expect("\uFB04".toLocaleUpperCase()).toBe("\u0046\u0046\u004C");
+    expect("\uFB05".toLocaleUpperCase()).toBe("\u0053\u0054");
+    expect("\uFB06".toLocaleUpperCase()).toBe("\u0053\u0054");
+    expect("\u0390".toLocaleUpperCase()).toBe("\u0399\u0308\u0301");
+    expect("\u03B0".toLocaleUpperCase()).toBe("\u03A5\u0308\u0301");
+    expect("\u1FB7".toLocaleUpperCase()).toBe("\u0391\u0342\u0399");
+    expect("\u1FC7".toLocaleUpperCase()).toBe("\u0397\u0342\u0399");
+    expect("\u1FF7".toLocaleUpperCase()).toBe("\u03A9\u0342\u0399");
+});