Breaking: #101469 - Introduce type declarations in FolderInterface 

Description 

Return and param type declarations have been introduced for all methods stubs of \TYPO3\CMS\Core\Resource\FolderInterface .

Impact 

In consequence, all implementations of \TYPO3\CMS\Core\Resource\FolderInterface need to reflect those changes and add the same return and param type declarations.

In case, any of the Core implementations are extended, overridden methods might need to be adjusted. The Core classes, implementing \TYPO3\CMS\Core\Resource\FolderInterface are:

• \TYPO3\CMS\Core\Resource\Folder
• \TYPO3\CMS\Core\Resource\InaccessibleFolder

Affected installations 

All installations that implement \TYPO3\CMS\Core\Resource\FolderInterface or that extend either \TYPO3\CMS\Core\Resource\Folder or \TYPO3\CMS\Core\Resource\InaccessibleFolder .

Migration 

Add the same param and return type declarations the interface does.