WebP images are not regenerated when using image_widget_crop

I attach a patch for the fix. After applying the patch, drush cr is needed.

The crop module (that the image_widget_crop is depending on) has a postSave function where it removes all the generated stylized image files for that image if I update a crop settings for that field. In this patch I add an entity update hook where if a crop entity is updated for an image, imageapi_optimize_webp removes all the generated webp images in every image style for that image. That way, next time when it's loaded in the browser, it'll be regenerated on the fly with using the new cropping settings.

That patch should also fix every filter's regeneration that is based on the crop module (such as focal point). Although I didn't test those, theoretically it should work.

A new patch: I added another thing: regenerate webp when the crop is created. If an image field already contains an image file and the crop widget is set in the form display later, then the applied crop settings will create a new crop entity. And if there's only an update hook and no insert hook for that crop entity, then the generated image styles won't be regenerated until I actually update an existing crop.

Right now, the module generates path in ImageAPIOptimizeWebPPipeline and WebP classes like this: mypic.jpg.webp.

Patch #7 won't work properly when the webp picture is already generated with the current naming. It is because it flushes image styles that have the path like that: mypic.webp and if the image was already generated in that style, then it has a path like that: mypic.jpg.webp.

First, issue #3203988: Don't add original file extension in webp versions of images needs to be fixed for patch #7 to work. Until that happens, patch #3 is advised to use.

The regenerating code should run after the \Drupal\image\Entity\ImageStyle::flush($path) is done.

1. If you pass the image $path parameter, then flushes that image's file in the current ImageStyle. This code is called in Drupal and contrib. The function doesn't create an event or calls a hook when that happens, so we cannot subscribe to anything then.
2. If you don't pass a value in the $path parameter, then it flushes all the files in the current ImageStyle's folder, and calls the image_style_flush hook. But that only happens when the image style configuration is changed, so rarely.

The only solution would be to alter the ImageStyle config entity class with a new one in this module. In this class we would only modify the flush() method by extending its code to flush the webp path.