3dsmax: startup fixes

[antirotor]

Brief description

This is fixing various issues that can occur on some of the 3dsmax versions.

Description

On displays with +4K resolution UI was broken, some 3dsmax versions couldn't process PYTHONPATH correctly. This PR is forcing sys.path and disabling QT_AUTO_SCREEN_SCALE_FACTOR

Testing notes:

1. 3dsmax with OpenPype should start as expected
2. No UI issues on high resolution displays

[moonyuet]

I dont have the 4k monitor but I test the code, it doesn't break Openpype working in the max host.
Also tested the suggested code on the startup.py. It also works and doesn't break the plugin working in the host.