ACP2E-1958: avoid reloading configs for each requested key; added unit tests

Author: alzota

lib/internal/Magento/Framework/App/DeploymentConfig.php

@@ -86,7 +86,6 @@ public function __construct(DeploymentConfig\Reader $reader, $overrideData = [])
      */
     public function get($key = null, $defaultValue = null)
     {
-        //if no key is requested, then all config is returned.
         if ($key === null) {
             if (empty($this->flatData)) {
                 $this->reloadData();
@@ -211,6 +210,8 @@ private function reloadData(): void
     }
 
     /**
+     * Load all getenv() configs once
+     *
      * @return array
      */
     private function getAllEnvOverrides(): array

lib/internal/Magento/Framework/Module/ModuleList.php

@@ -140,8 +140,9 @@ public function isModuleInfoAvailable()
      */
     private function loadConfigData()
     {
-        if (null === $this->configData && null !== $this->config->get(ConfigOptionsListConstants::KEY_MODULES)) {
-            $this->configData = $this->config->get(ConfigOptionsListConstants::KEY_MODULES);
+        $config = $this->config->get(ConfigOptionsListConstants::KEY_MODULES);
+        if (null === $this->configData && null !== $config) {
+            $this->configData = $config;
         }
     }