perf: add config Optimize and move $configCacheEnabled

The Cache Config class that extends BaseConfig is very slow to instantiate..
See #8558 (comment)

Author: kenjis

app/Config/Cache.php

@@ -168,13 +168,4 @@ class Cache extends BaseConfig
      * @var bool|list<string>
      */
     public $cacheQueryString = false;
-
-    /**
-     * --------------------------------------------------------------------------
-     * Config Caching
-     * --------------------------------------------------------------------------
-     *
-     * @see https://codeigniter.com/user_guide/concepts/factories.html#config-caching
-     */
-    public bool $configCacheEnabled = false;
 }

app/Config/Optimize.php

@@ -0,0 +1,23 @@
+<?php
+
+namespace Config;
+
+/**
+ * Optimization Configuration.
+ *
+ * NOTE: This class does not extend BaseConfig for performance reasons.
+ *       So you cannot replace the property values with Environment Variables.
+ *
+ * @immutable
+ */
+class Optimize
+{
+    /**
+     * --------------------------------------------------------------------------
+     * Config Caching
+     * --------------------------------------------------------------------------
+     *
+     * @see https://codeigniter.com/user_guide/concepts/factories.html#config-caching
+     */
+    public bool $configCacheEnabled = false;
+}

system/Boot.php

@@ -17,8 +17,8 @@
 use CodeIgniter\CLI\Console;
 use CodeIgniter\Config\DotEnv;
 use Config\Autoload;
-use Config\Cache;
 use Config\Modules;
+use Config\Optimize;
 use Config\Paths;
 use Config\Services;
 
@@ -55,7 +55,8 @@ public static function bootWeb(Paths $paths): int
         static::setExceptionHandler();
         static::initializeKint();
 
-        $configCacheEnabled = (new Cache())->configCacheEnabled ?? false;
+        $configCacheEnabled = class_exists(Optimize::class)
+            && (new Optimize())->configCacheEnabled;
         if ($configCacheEnabled) {
             $factoriesCache = static::loadConfigCache();
         }

user_guide_src/source/concepts/factories.rst

@@ -318,7 +318,7 @@ How to Enable Config Caching
 
 .. versionadded:: 4.5.0
 
-Set the following property to ``true`` in **app/Config/Cache.php**::
+Set the following property to ``true`` in **app/Config/Optimize.php**::
 
     public bool $configCacheEnabled = true;