[v7.0] Refactor and modernize image gallery

[freshworkx]

This will be a breaking change in the new major version.

• extend own model from Core FileCollection so that all properties are available in one place.
• this makes TransferCollectionInfo class superfluous, which is actually more of a DTO.
• remove own Filefactory class and replace it with the corresponding Core class.
• modernize controller, repository and templates according to the current documentation v12/v13
• prevent unnecessary database queries, check caching options to improve speed
• work with file references and pay attention to crop variants
• all plugins remain unchanged so that change is backwards compatible with existing installations

See corresponding documentation
https://docs.typo3.org/m/typo3/reference-coreapi/12.4/en-us/ApiOverview/Fal/Collections/Index.html