perf: add Factories::get() v2

[kenjis]

Description
Supersedes #8598

• add Factories::get() method to get the shared instance fast.
• config() uses Factories::get()

I benchmarked #8598 and this PR on the Welcome page and there were no significant differences in the numbers.

4.5:

$ wrk -t10 -d5s http://localhost/CodeIgniter4/
Running 5s test @ http://localhost/CodeIgniter4/
  10 threads and 10 connections
  Thread Stats   Avg      Stdev     Max   +/- Stdev
    Latency     2.19ms    1.48ms  23.59ms   92.93%
    Req/Sec   492.21    112.11     1.11k    60.36%
  24613 requests in 5.10s, 410.38MB read
Requests/sec:   4826.10
Transfer/sec:     80.47MB

This PR:

$ wrk -t10 -d5s http://localhost/CodeIgniter4/
Running 5s test @ http://localhost/CodeIgniter4/
  10 threads and 10 connections
  Thread Stats   Avg      Stdev     Max   +/- Stdev
    Latency     2.19ms    1.56ms  29.09ms   92.07%
    Req/Sec   497.06    106.24   676.00     57.00%
  24766 requests in 5.01s, 412.93MB read
Requests/sec:   4941.45
Transfer/sec:     82.39MB

diff --git a/app/Config/Services.php b/app/Config/Services.php
index df7c8ad086..f32b15b38a 100644
--- a/app/Config/Services.php
+++ b/app/Config/Services.php
@@ -2,6 +2,8 @@
 
 namespace Config;
 
+use CodeIgniter\Autoloader\FileLocator;
+use CodeIgniter\Autoloader\FileLocatorCached;
 use CodeIgniter\Config\BaseService;
 
 /**
@@ -19,14 +21,16 @@ use CodeIgniter\Config\BaseService;
  */
 class Services extends BaseService
 {
-    /*
-     * public static function example($getShared = true)
-     * {
-     *     if ($getShared) {
-     *         return static::getSharedInstance('example');
-     *     }
-     *
-     *     return new \CodeIgniter\Example();
-     * }
-     */
+    public static function locator(bool $getShared = true)
+    {
+        if ($getShared) {
+            if (! isset(static::$instances['locator'])) {
+                static::$instances['locator'] = new FileLocatorCached(new FileLocator(static::autoloader()));
+            }
+
+            return static::$mocks['locator'] ?? static::$instances['locator'];
+        }
+
+        return new FileLocator(static::autoloader());
+    }
 }
diff --git a/preload.php b/preload.php
index 63c781c220..73ae062668 100644
--- a/preload.php
+++ b/preload.php
@@ -49,7 +49,7 @@ class preload
      */
     private array $paths = [
         [
-            'include' => __DIR__ . '/vendor/codeigniter4/framework/system',
+            'include' => __DIR__ . '/system',
             'exclude' => [
                 // Not needed if you don't use them.
                 '/system/Database/OCI8/',
@@ -69,6 +69,11 @@ class preload
                 '/system/ThirdParty/',
             ],
         ],
+        [
+            'include' => __DIR__ . '/vendor',
+            'exclude' => [],
+        ],
+
     ];
 
     public function __construct()
diff --git a/public/index.php b/public/index.php
index 8cf5ce347c..eacaec8791 100644
--- a/public/index.php
+++ b/public/index.php
@@ -49,8 +49,8 @@ if (! defined('ENVIRONMENT')) {
 }
 
 // Load Config Cache
-// $factoriesCache = new \CodeIgniter\Cache\FactoriesCache();
-// $factoriesCache->load('config');
+$factoriesCache = new CodeIgniter\Cache\FactoriesCache();
+$factoriesCache->load('config');
 // ^^^ Uncomment these lines if you want to use Config Caching.
 
 /*
@@ -79,7 +79,7 @@ $app->setContext($context);
 $app->run();
 
 // Save Config Cache
-// $factoriesCache->save('config');
+$factoriesCache->save('config');
 // ^^^ Uncomment this line if you want to use Config Caching.
 
 // Exits the application, setting the exit code for CLI-based applications

$ sudo service apache2 restart
$ sudo service apache2 status

$ cat /etc/lsb-release 
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=22.04
DISTRIB_CODENAME=jammy
DISTRIB_DESCRIPTION="Ubuntu 22.04.3 LTS"

$ apache2 -v
Server version: Apache/2.4.52 (Ubuntu)
Server built:   2023-10-26T13:44:44

$ php -v
PHP 8.1.2-1ubuntu2.14 (cli) (built: Aug 18 2023 11:41:11) (NTS)
Copyright (c) The PHP Group
Zend Engine v4.1.2, Copyright (c) Zend Technologies
    with Zend OPcache v8.1.2-1ubuntu2.14, Copyright (c), by Zend Technologies

Checklist:

• Securely signed commits
• Component(s) with PHPDoc blocks, only if necessary or adds value
• Unit testing, with >80% coverage
• User guide updated
• Conforms to style guide

[paulbalandan]

Is this really non-existent?

[kenjis]

No. Thanks!
Fixed the method name.