Update ui.py show megapixels calc

[sean1138]

just an idea i had and was able to actually make this work in my local UI. I'm not proficient in any programming language though so i don't know about making this same change everywhere else in the code base as appropriate.

if this is even something anyone other than myself would like to see.

Description

• add calculated megapixels value to hires fix info shown in ui
• added simple and i think correct multiply and divide code to get the expected megapixel vlaue after a hires "upscale by" setting change
• doesn't really fix any problem, just something i think would be neat to see

Screenshots/videos:

Checklist:

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

[zrichz]

I don't think the UI needs to be cluttered by 3 decimal places. the nearest megapixel might be more appropriate if this is to be implemented

[w-e-w]

I personally don't think this to be useful at least I cannot think of a use case

[AUTOMATIC1111]

Similarly to w-e-w I don't think this is useful.