Preload data when using Dex.mod (#10641)

* Preload data when using Dex.mod

With the initial introduction fo TypeScript at 3716f36,
``Dex.mod``, and ``Dex.format`` (nowadays ``Dex.forFormat``)
no longer ensured that the data cache has been filled.

Newer lazy-loading getter APIs were introduced, which were
intended to be used as a replacement for direct access to the
loaded data (``dataCache``).

However, these APIs were either not effective or not properly
used., as reflected by 43ef4d9, which reverted ``Dex.forFormat``
to its full capabilities.

Nevertheless, ``Dex.mod`` was left untouched, which results in a
footgun where ``Dex.forFormat('gen1randbats').gen == 1``, but
``Dex.mod('gen1').gen == 9``.

This commit brings back ``Dex.mod`` to its original behavior, so
that gen information is always there when it's needed.

* Add test for dex.mod(mod).gen

* Swap around test instructions

This is more reliable given the load order.

sim/dex.ts

@@ -165,7 +165,7 @@ export class ModdedDex {
 
 	mod(mod: string | undefined): ModdedDex {
 		if (!dexes['base'].modsLoaded) dexes['base'].includeMods();
-		return dexes[mod || 'base'];
+		return dexes[mod || 'base'].includeData();
 	}
 
 	forGen(gen: number) {

test/sim/dex.js

@@ -3,6 +3,14 @@
 const assert = require('./../assert');
 
 describe('Mod loader', function () {
+	it('should always provide accurate gen information', function () {
+		{
+			const Dex = require('./../../dist/sim/dex').Dex;
+			assert.equal(Dex.mod('gen2').gen, 2);
+			assert.equal(Dex.forFormat('gen1randombattle').gen, 1);
+		}
+	});
+
 	it('should work fine in any order', function () {
 		{
 			const Dex = require('./../../dist/sim/dex').Dex;