Large images posted in comments break out of layout when shown in the admin

[mattheu]

If a comment is submitted that contains a very large image, it is shown at full size and looks a bit broken.

In the screenshots below, part of the image is hidden as it larger than the width of the column. Also it makes it very tall and requires a lot of scrolling.

This is even more of an issue on mobiles, as even moderately sized images will break out of the contianer.

Comments containing very large images should probably not be posted at all - but I would say that is a separate issue.

[SergeyBiryukov]

In 27252:

Prevent large images in comments from overflowing the meta box.

props mattheu.
fixes #26643.