Task linked: OP-7596 3dsmax: unit scale issue for FBX

Well in short, doesnt work for me...

Tested just in legacy OP and max 2024 I first tested the default Inches setting and then metric millimeters but neither worked well.

The max scene still showing generic measureless units and not the one set in OP Settings.

Also the Set Units Scale menu action doesnt work at all.

What I have expected: when set in OP Settings some `unit type` that the workfile adopts it immedeatelly when created and/or if needed on already saved workfile to be able to use menu action `set units scale` to properly set the units according to OP Settings.

Right now it does not do any of these?

Have you checked if it aligns with the unit scale setting in OP by clicking System unit setup?

I just find out the issue and it seems it doesn't align with the unit scale, will fix it right away

@LiborBatek the latest commit would use the metric types for unit scale and it is set accordingly with the project settings.

@LiborBatek the latest commit would use the metric types for unit scale and it is set accordingly with the project settings.

Will that change count also for other unit systems too? like US etc?

Only metric system being supported right now.

Right now, Set Unit Scale in the OP Settings correctly used when triggering action from OP Menu Set Unit Scale.

Note: Right now the OP Settings not being propagated on initial host launch which would be also preffered, but this PR do what it should in general.

I am creating an issue for this and keep it as record. The #postSystemStartup callback is still not working as expected (like what it does in the past) so currently we can't propagate the setting during the launch.
See: https://www.scriptspot.com/forums/3ds-max/general-scripting/callback-postsystemstartup-not-working
https://discourse.techart.online/t/maxscript-scripted-material-plugins-and-callbacks/2055

@antirotor would you mind take a glance at the code to see anything needs specific change? Thanks!

Code concerning units changes looks good, but I have slight objection against changes in the event system within this PR - if I read it correctly, the changes have nothing to do with the actual unit scale issue. If the automatic change of units during the startup cannot be done because some issue with events, I wouldn't include these changes here at all and move them to separate issue/PR

I have restored the code for event system, and we can wait to refactor it when the postSystemStartup callback has been fixed.