Sanitize strings properly

Core sanitization functions:

• AIPromptSegmentBase::buildPreview() - returns markup render element with html converted to html entities, and with br tags allowed only (new lines)
• AIPromptSegmentBase::render() - returns raw not sanitized string for sending to AI in its original any kind of form (it is not displayed to the user directly)
• AIPromptCommonEngineeringForm::displayOutputSubmit() - helper function to display prompt output for the user. Output is displayed either with ksm function if devel module is enabled, or with $this->messenger()->addMessage($this->prepareStatusMessage($output))
• AIPromptCommons::prepareStatusMessage() - html is escaped and new line BR tags are added, Drupal\Core\Render\Markup is returned

Automatically closed - issue fixed for 2 weeks with no activity.