Media/Upload: When the users upload big images and WordPress creates a scaled...

Media/Upload: When the users upload big images and WordPress creates a scaled image to use as the largest size, append `scaled-` to the file names of the scaled images to make them easier to recognize.

Props kraftbj, azaozz.
Fixes #48304.
Built from https://develop.svn.wordpress.org/trunk@46565


git-svn-id: https://core.svn.wordpress.org/trunk@46362 1a063a9b-81f0-0310-95a4-ce76da25c4cd