Feature: #64257 - Support multiple UID in PageRepository::getMenu()

Description

An array of uid values can be passed to PageRepository::getMenu(), providing the chance to build menus from several roots.

Example: Fetch children of pages #2 and #3:

$pageRepository = new \TYPO3\CMS\Frontend\Page\PageRepository();
$pageRepository->init(false);
$rows = $pageRepository->getMenu(array(2, 3));