Kajiya should not render at a lower resolution on HiDPI screens

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Describe the bug
Kajiya currently explicitly specifies that on HiDPI screens, the viewport will be sized using logical pixels rather than physical pixels.

To Reproduce
Steps to reproduce the behavior:

1. run any app that uses kajiya

Expected behavior
Rendering should be performed in physical pixels and not upscaled. Upscaling (using DLSS, FSR, etc.) should be an explicit choice and not forced based on the display DPI.

Screenshots
Edges look pretty bad on my 4K display:

Additional context
I'm using an old commit of Kajiya for cornell-mcray but AFAICT this 'feature' has remained the same since then.

AFAIK, the main reason to do this is to reduce GPU requirements for weak computers- i.e. the highest-resolution displays, like 4K, are almost always paired with even a lack of any GPU at all- but this way of doing it looks terrible, even compared to simply having a perfect 1080p display in the first place.