This allow for more granular requests reducing the engine
startup time in case sub-process compilation is not enabled
(when it is enabled, gains are not substantial).
This also makes engine startup less blocking.
The batches are only requested if needed.
Some of the batches can only be requested after object sync.
Given we don't have a priority system for the shader compilation
queue, the engine shader ends up compiling after the scene
ones.
The remaining blocking is the texture loading and geometry loading.
The world compilation is still blocking in this patch to avoid making it
more complex. But this can be another optimization we can do later on.
See PR for performance numbers.
Pull Request: https://projects.blender.org/blender/blender/pulls/139454
b89c36f0e7