Issue #3347750: Allow Modules and Themes to define component directories

src/ComponentPluginManager.php

@@ -298,7 +298,7 @@ class ComponentPluginManager extends DefaultPluginManager {
       ...$this->moduleHandler->getModuleDirectories(),
       ...$this->themeHandler->getThemeDirectories(),
     ];
-    return array_map(
+    $directories = array_map(
       static fn(string $path) => rtrim(sprintf(
         '%s%s%s',
         rtrim($path, DIRECTORY_SEPARATOR),
@@ -307,6 +307,10 @@ class ComponentPluginManager extends DefaultPluginManager {
       ), DIRECTORY_SEPARATOR),
       $extension_directories
     );
+    // Allow modules and themes to alter the directories.
+    $this->moduleHandler->alter('cl_components_directories', $directories);
+    $this->themeManager->alter('cl_components_directories', $directories);
+    return $directories;
   }
 
   /**