[underscore] Fixes sortBy on chained array wrapper (#40417)

* underscore - Fix an issue where calling sortBy on a chained wrapper around Z[] claimed to return a Z.

e.g. _.chain([1, 2, 3]).sortBy(x => -x).value() would claim to be of type number, not number[].

* underscore - Ensure length property is present on value of calling sortBy on chained, wrapped array.

* underscore - Be more explicit that sortBy returns an array.

That's its implementation behaviour, even if not provided with an array to begin with.

* underscore - Revert unused generic type.

types/underscore/index.d.ts

@@ -5306,13 +5306,13 @@ declare module _ {
         * Wrapped type `any[]`.
         * @see _.sortBy
         **/
-        sortBy(iterator?: _.ListIterator<T, any>, context?: any): _Chain<T>;
+        sortBy(iterator?: _.ListIterator<T, any>, context?: any): _Chain<T, T[]>;
 
         /**
         * Wrapped type `any[]`.
         * @see _.sortBy
         **/
-        sortBy(iterator: string, context?: any): _Chain<T>;
+        sortBy(iterator: string, context?: any): _Chain<T, T[]>;
 
         /**
         * Wrapped type `any[]`.

types/underscore/underscore-tests.ts

@@ -196,6 +196,11 @@ _.min(numbers);
 
 _.sortBy([1, 2, 3, 4, 5, 6], (num) => Math.sin(num));
 
+_([1, 2, 3]).chain()
+    .sortBy(x => -x)
+    .sortBy(x => -x)
+    .value().length;
+
 _([1.3, 2.1, 2.4]).groupBy((e) => Math.floor(e));
 _.groupBy([1.3, 2.1, 2.4], (num) => Math.floor(num).toString());
 _.groupBy(['one', 'two', 'three'], 'length');