Add filter or option to Import Image Stack to pad images to a certain Width/Height

This could be automated so the filter gets the largest dimensions of width and height by looking at all the images first, then padding the images to that maximum width/height, then finally doing the import.
This would require the preflight to examine each image in the series for its width/height which might slow down the preflight significantly for large image series. This slow down needs to be weighed by the benefits of adding the options. Maybe as a checkbox option and with some caching of the images the first preflight might take some time but after that it should be fast as long as the files are not changed.

定位 Import Image Stack filter 及其 preflight 路径。检查如何获取图像序列中各图像的尺寸，然后评估用于 preflight 和导入流程的 opt-in padding 选项与缓存。完成标准是：无需进行不必要的重复工作，即可将序列填充到所请求的宽度和高度，或最大宽度和高度。

由索引模型根据 Issue 内容生成。