[BUGFIX] Improve performance by lazy loading of thumbnails

Adds the loading="lazy" HTML attribute to a couple
of img tags, used to display thumbnails in the backend.

This will improve performance, especially for larger
listings, e.g. in the filelist module.

Resolves: #102501
Releases: main, 12.4
Change-Id: I5f4b7c37786e8f4283bb997f40c501f09984e410
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/82011


Tested-by: core-ci <typo3@b13.com>
Tested-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Oliver Bartsch <bo@cedev.de>