ACPT-1599: Fixing DeploymentConfig resets & reloads every time new key that wasn't previously set

Fixing problem ACP2E-2198.

```
[Progress: 861 / 864]
Disabling Maintenance Mode:

In ResourceConnection.php line 162:

[DomainException]
Connection "default" is not defined
```

    The root cause of problem is that the `Disabling Maintenance Mode` part of the install uses the first created DeploymentConfig object created in the process, which doesn't get updated, while before that runs, different part of the install that writes to the config is using the second DeploymentConfig object that was created by Laminas ServiceManager.  The reason why this happens is because Intercepters use ObjectManager::getInstance to get the ObjectManager to find PluginList.  This causes the plugins to use the first DeploymentConfig object which was created for the first ObjectManager.  Other objects that use ObjectManager::getInstance may have this problem as well.

    This commit adds a workaround in main loop of Installer that calls DeploymentConfig::resetData() on the original DeploymentConfig.

Author: JacobBrownAustin

setup/src/Magento/Setup/Model/Installer.php

@@ -12,10 +12,12 @@
 use Magento\Framework\App\Cache\Type\Block as BlockCache;
 use Magento\Framework\App\Cache\Type\Config as ConfigCache;
 use Magento\Framework\App\Cache\Type\Layout as LayoutCache;
+use Magento\Framework\App\DeploymentConfig;
 use Magento\Framework\App\DeploymentConfig\Reader;
 use Magento\Framework\App\DeploymentConfig\Writer;
 use Magento\Framework\App\Filesystem\DirectoryList;
 use Magento\Framework\App\MaintenanceMode;
+use Magento\Framework\App\ObjectManager;
 use Magento\Framework\App\State\CleanupFiles;
 use Magento\Framework\Component\ComponentRegistrar;
 use Magento\Framework\Config\ConfigOptionsListConstants;
@@ -175,10 +177,15 @@ class Installer
     private $installInfo = [];
 
     /**
-     * @var \Magento\Framework\App\DeploymentConfig
+     * @var DeploymentConfig
      */
     private $deploymentConfig;
 
+    /**
+     * @var DeploymentConfig
+     */
+    private $firstDeploymentConfig;
+
     /**
      * @var ObjectManagerProvider
      */
@@ -327,6 +334,11 @@ public function __construct(
         $this->phpReadinessCheck = $phpReadinessCheck;
         $this->schemaPersistor = $this->objectManagerProvider->get()->get(SchemaPersistor::class);
         $this->triggerCleaner = $this->objectManagerProvider->get()->get(TriggerCleaner::class);
+        /* Note: Because this class is dependency injected with Laminas ServiceManager, but our plugins, and some
+         * other classes also use the App\ObjectManager instead, we have to make sure that the DeploymentConfig object
+         * from that ObjectManager gets reset as different steps in the installer will write to the deployment config.
+         */
+        $this->firstDeploymentConfig = ObjectManager::getInstance()->get(DeploymentConfig::class);
     }
 
     /**
@@ -381,6 +393,9 @@ public function install($request)
         $this->log->log('Starting Magento installation:');
 
         foreach ($script as $item) {
+            /* Note: Because the $this->DeploymentConfig gets written to, but plugins use $this->firstDeploymentConfig,
+             * we have to reset this one after each item of $script so the plugins will see the config updates. */
+            $this->firstDeploymentConfig->resetData();
             list($message, $method, $params) = $item;
             $this->log->log($message);
             try {