Clear Caches button is now separate from the performance form

Summary

The "Clear all caches" button has been moved into a separate form. Removing this functionality from the performance configuration form allows caches to be cleared without any possible side effects triggered by saving performance configuration. This could impact any custom or contrib modules using hook_form_alter to modify the "Clear all caches" button behavior.

Before

function example_module_form_system_performance_settings_alter(&$form, \Drupal\Core\Form\FormStateInterface $form_state, $form_id) {
  // Alter cache clear button...
}

After

function example_module_form_system_clear_cache_alter(&$form, \Drupal\Core\Form\FormStateInterface $form_state, $form_id) {
  // Alter cache clear button...
}