Now you can define custom groups for the chests, as shown in the trapped
chests example (now they show up under "Mechanisms" tab in creative!).
I'm a bit suspicious of the new return-wrapped functions, as in *they
might break under some circumstances I didn't observe*. It will require
some heavy testing to make sure nothing crashes in the future.
Also, `on_rightclick` for double chests is something I really want to
return-wrap as well, but failed to do so. 🤷
Pass chest entity initialization data to on_activate as staticdata so
initialization is atomic, preventing premature deletion of chest entity
by concurrent server steps.
