propagate launch context environment to generate project ue workers

[nebukadhezer]

Changelog Description

When generating a project from scratch the creation fails as the Ayon unreal init attempts to import ayon_core.

Additional review information

Need to investigate if this also needs UE_PYTHONPATH or not.

Testing notes:

1. blank project one setup task
2. launch unreal for the first time on a the setup task
3. generation fails with no module found ayon_core

[nebukadhezer]

would close #263

[nebukadhezer]

So in order for this to work, all must be provided to UE_PYTHONPATH... we could add this in front of the call, but I am hesitant if that is a good idea with my testing all Ayon related python modules are already in UE_PYTHONPATH, for my rez stuff I can easily solve that in the unreal package.py and pipe all in there then all is working.
the most comprehensive move would be to merge UE_PYTHONPATH with PYTHONPATH and make sure all is in there... but that is a choice I am leaving up to you to decide.
This will work if beforehand everyone makes sure to provide unreal relevant python modules via UE_PYTHONPATH, which to me is acceptable behaviour.

[moonyuet]

the most comprehensive move would be to merge UE_PYTHONPATH with PYTHONPATH and make sure all is in there... but that is a choice I am leaving up to you to decide.

You already did this when implementing #264 as shown in https://github.com/dev-holobay/ayon-unreal/blob/ebd10367bca9414ed528825126c777265b58602a/client/ayon_unreal/hooks/pre_pyside_install.py#L222-L228. 😃

[moonyuet]

I tested in 5.4. it is working. I will test 5.7 later.

[moonyuet]

Tested successfully in 5.7