TYPO3 Core

While searching for a way to get a comma-seperated PID list without using the old pi_getPidList function (defined in TYPO3\CMS\Frontend\Plugin\AbstractPlugin) I found three definitions of a function getTreeList in different classes:

1. in TYPO3\CMS\Core\Database\QueryGenearator
2. in TYPO3\CMS\Core\Database\QueryView
3. in TYPO3\CMS\Frontend\ContentObject\ContentObjectRenderer

The first two getTreeList are almost equal (and have a "todo: Define visibility"). Each of these methods is public. Perhaps it would be useful to have a utility function doing this, inspired by the method defined in the ContentObjectRenderer because that one seems to use caching.

This is related to #33138: Provide getPidList function in ExtBase environment (includes propsed solution)