Fix inpaint only masked pixels are shifted

[light-and-ray]

Description

Fixes bug: pasted image is shifted right and down on factor number of pixels after it was upscaled by this factor

This bug wasn't seen very often because rounded scale factor was almost always 1, and mask blur by default hides this artifact

Also this PR adds option to correct padding to have integer upscale on applying overlay

Screenshots/videos:

Original:

Options: padding=28, mask_blur=0, resolution=451x451, bad quality because I've used LCM, do not care about it

Old behavior:

Integer option on, but bug exists:

Here scale factor become 2, and it started look like a disaster. And this can happen and happens in current behavior anciently, if scale factor > 1 and upscale non integer

Integer option on and fixed bug:

Because this integer upscale correction can increase padding on 50-150 pixels, I've made it optional. If option is off, result is still better then the old behavior, but upscale is not integer (worse fit, better resolution):

Integer option off and fixed bug:

Checklist:

• I have read contributing wiki page
• I have performed a self-review of my own code
• My code follows the style guidelines
• My code passes tests

[light-and-ray]

I have added a threshold. Because I can't find any other idea why it happens in 256p, except maybe due to lower resolution is 1st case - more details are gone. I find it logical

Also I saw this problem that @w-e-w you found in action, after I added aspect ratio correction in my extension which I mentioned above. It sometimes became less then 300-400 pч
+ I have deleted integer_only_masked option in the new commit, because it's not really useful, and buggy.