LibJS: Implement the Temporal.Duration constructor

This also includes a stubbed Temporal.Duration.prototype.

Until we have re-implemented Temporal.PlainDate/ZonedDateTime, some of
Temporal.Duration.compare (and its invoked AOs) are left unimplemented.

Libraries/LibJS/Tests/builtins/Temporal/Duration/Duration.compare.js

@@ -0,0 +1,95 @@
+describe("correct behavior", () => {
+    test("length is 2", () => {
+        expect(Temporal.Duration.compare).toHaveLength(2);
+    });
+
+    function checkCommonResults(duration1, duration2) {
+        expect(Temporal.Duration.compare(duration1, duration1)).toBe(0);
+        expect(Temporal.Duration.compare(duration2, duration2)).toBe(0);
+        expect(Temporal.Duration.compare(duration1, duration2)).toBe(-1);
+        expect(Temporal.Duration.compare(duration2, duration1)).toBe(1);
+    }
+
+    test("basic functionality", () => {
+        const duration1 = new Temporal.Duration(0, 0, 0, 1);
+        const duration2 = new Temporal.Duration(0, 0, 0, 2);
+        checkCommonResults(duration1, duration2);
+    });
+
+    test("duration-like objects", () => {
+        const duration1 = { years: 0, months: 0, weeks: 0, days: 1 };
+        const duration2 = { years: 0, months: 0, weeks: 0, days: 2 };
+        checkCommonResults(duration1, duration2);
+    });
+
+    test("duration strings", () => {
+        const duration1 = "P1D";
+        const duration2 = "P2D";
+        checkCommonResults(duration1, duration2);
+    });
+});
+
+describe("errors", () => {
+    test("invalid duration-like object", () => {
+        expect(() => {
+            Temporal.Duration.compare({});
+        }).toThrowWithMessage(TypeError, "Invalid duration-like object");
+
+        expect(() => {
+            Temporal.Duration.compare({ years: 0, months: 0, weeks: 0, days: 1 }, {});
+        }).toThrowWithMessage(TypeError, "Invalid duration-like object");
+    });
+
+    test("relativeTo is required for comparing calendar units (year, month, week)", () => {
+        const duration1 = new Temporal.Duration(1);
+        const duration2 = new Temporal.Duration(2);
+
+        expect(() => {
+            Temporal.Duration.compare(duration1, duration2);
+        }).toThrowWithMessage(
+            RangeError,
+            "A starting point is required for comparing calendar units"
+        );
+
+        const duration3 = new Temporal.Duration(0, 3);
+        const duration4 = new Temporal.Duration(0, 4);
+
+        expect(() => {
+            Temporal.Duration.compare(duration3, duration4);
+        }).toThrowWithMessage(
+            RangeError,
+            "A starting point is required for comparing calendar units"
+        );
+
+        const duration5 = new Temporal.Duration(0, 0, 5);
+        const duration6 = new Temporal.Duration(0, 0, 6);
+
+        expect(() => {
+            Temporal.Duration.compare(duration5, duration6);
+        }).toThrowWithMessage(
+            RangeError,
+            "A starting point is required for comparing calendar units"
+        );
+
+        // Still throws if year/month/week of one the duration objects is non-zero.
+        const duration7 = new Temporal.Duration(0, 0, 0, 7);
+        const duration8 = new Temporal.Duration(0, 0, 8);
+
+        expect(() => {
+            Temporal.Duration.compare(duration7, duration8);
+        }).toThrowWithMessage(
+            RangeError,
+            "A starting point is required for comparing calendar units"
+        );
+
+        const duration9 = new Temporal.Duration(0, 0, 9);
+        const duration10 = new Temporal.Duration(0, 0, 0, 10);
+
+        expect(() => {
+            Temporal.Duration.compare(duration9, duration10);
+        }).toThrowWithMessage(
+            RangeError,
+            "A starting point is required for comparing calendar units"
+        );
+    });
+});