Readonly/private constructor-promoted service properties break DependencySerializationTrait (fatal errors + PHPStan failures)

Problem/Motivation

Several classes declare injected services as private or private readonly/protected readonly constructor-promoted properties, but all extend base classes (FormBase, ConfigFormBase, ConfirmFormBase, EntityListBuilder) using core's DependencySerializationTrait. Its __wakeup() reassigns service properties from the parent's scope after unserialization — it can't see private properties at all, and can't reinitialize readonly ones (PHP only allows one-time init from the declaring class's own scope). Result: fatal errors on readonly properties, and silent serialization breakage + PHPStan errors (dependencySerializationTraitProperty.unsupportedPrivateProperty/unsupportedReadOnlyProperty) on private ones.

  Error: Cannot initialize readonly property Drupal\ai_audio_generator\Form\SettingsForm::$entityTypeManager from scope                   
  Drupal\Core\Form\FormBase in Drupal\Core\Form\FormBase->__wakeup()                                                                      

Affected files:

• Form/SettingsForm.php (fixed here)
• Form/NodeAudioGenerateForm.php
• Form/PronunciationDictionaryNodeQuickAddForm.php
• Form/PronunciationDictionaryPromoteForm.php
• Form/PronunciationDictionaryQuickAddForm.php
• Form/PronunciationDictionarySearchForm.php
• PronunciationDictionaryEntryListBuilder.php

Proposed resolution

Change every affected property from private/private readonly/protected readonly to plain protected:

  -    protected readonly EntityTypeManagerInterface $entityTypeManager,                                                                  
  +    protected EntityTypeManagerInterface $entityTypeManager,