LayoutLMv2Processor: ensure 1-to-1 mapping between images and samples in case of overflowing tokens (#17092)
* add get_overflowing_images function to ensure 1-to-1 mapping between samples and images in LayoutLMv2Processor
* make style
* add test for overflowing_tokens, change assert to ValueError, avoiding unrelated formatting changes
* change line length by passing --preview into black