[Feature Request] Provide option to upscale to standard resolutions (FHD, 4K, etc.)

[srad]

Right now users have to define the output resolution via a percentage value.
This leads to the issue that you have to calculate the upscale factor by hand to achieve a certain resolution and in some cases it's not possible to precisely achieve this with the current function.

However, a better solution is to provide the option for the target resolutions: 1080p, 4k, custom, etc.
The user should not have to make calculations which cannot be specified anyway precisely in the given format, which often does not allow to reach the exact target resolution anyways.