[BUGFIX] Ensure scaled image size width/height are integers

Given the input width/heigth, getImageScale can return either int or float, depending of the calculated sizes.

This can triggers strict type warnings in calling code,
if width/heigth are expected to be integers.

In order to fix this, returned width/height are now always integers.

Resolves: #100076
Releases: main, 11.5
Change-Id: Ic29ba67f80a3a11a00a5b66f2644f923fa765064
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/78057


Tested-by: core-ci <typo3@b13.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>