Add a resizer similar to Avisynth's CropResize

[ghost]

It's possible to do resizing with zero aspect ratio error by utilizing subpixel cropping, a way to handle this automatically would be very useful.

[NSQY]

https://forum.doom9.org/showthread.php?p=1991790#post1991790

[ghost]

implemented myself here https://gist.github.com/wiwaz/7d5afee6aadb1dae0131aedc6d1a6440

[ghost]

Additionally, this is more fit for vskernels and just having an argument such as keepaspect to enable this behavior. It's almost always desirable over distorting the aspect ratio so maybe it should be default, too.

[Setsugennoao]

how would this work when you're specifying your own shift/src_xxx

[ghost]

The script adjusts existing values (if present) so theres no issue with user provided shifts or regions.

[Setsugennoao]

Fixed here Jaded-Encoding-Thaumaturgy/vs-kernels@e94adb9