Save Layer (expanded/collapsed) state during save so it can be restored on open

Feature description

Save Layer (expanded/collapsed) state during save so it can be automaticly restored on open

Annoying little bug.... I got a ton of layer groups and some are expanded and some are collapsed this id done to be easy to toggle visability of different layer groups

when saved and closing the .qgz file the E/C Layer state is not saved when the .qgz file is reopened, it seems the first subgroup is always expanded.

This is anoying when opening multiple files... It actually takes significant time to scroll and expand and collapse groups to get the appearance you want when you saved

Additional context

Before Save and Reload file

After Save and Reload File

Would like it to open in the same state as it was saved