[FEATURE_REQUEST] "scale to longest" and "scale to shortest"

[the-liquid-metal]

It is common for photosets to have both landscape and protrait orientation. At the moment, realesrgan-gui, just has "scale to width" and "scale to height" options. It is impractical to upscale these photosets with realesrgan-gui. First we have to group each files into orientation, upscale, and last regroup again. It would be better if there are "scale to longest" and "scale to shortest" options available.

• "scale to longest" means dimension which has longer value will be set to new value.
• "scale to shortest" means dimension which has shorter value will be set to new value.

for example:

• if i have image with 900 x 700, and i set "scale to longest" to 4096, the output is 4096 x 3185.
• if i have image with 700 x 900, and i set "scale to longest" to 4096, the output is 3185 x 4096.
• if i have image with 980 x 720, and i set "scale to shortest" to 4096, the output is 5575 x 4096.
• if i have image with 720 x 980, and i set "scale to shortest" to 4096, the output is 4096 x 5575.

These new options will preserve size consistency among photoset items.

It's better to have a single selection control with items: "width", "height", "longest", "shortest", and a single numeric control, rather than 4 radio controls and 4 numeric controls.

[the-liquid-metal]

Tested. It works great. Thank you.