Add 50lb flour and sugar bags to the world

[Maleclypse]

Summary

None

Purpose of change

Adds 50lb bags of sugar and flour into the world.

Describe the solution

Add new bag, and two item groups using it.

Describe alternatives you've considered

None

Testing

Additional context

[akrieger]

([slow] ~starting_items)=> (continued from above) ERROR : src/item_factory.cpp:2759 [void Item_factory::check_definitions() const] warnings for type bag_paper_powder_50lb:
([slow] ~starting_items)=> is bigger on the inside. consider using TARDIS flag.

[Maleclypse]

([slow] ~starting_items)=> (continued from above) ERROR : src/item_factory.cpp:2759 [void Item_factory::check_definitions() const] warnings for type bag_paper_powder_50lb:
([slow] ~starting_items)=> is bigger on the inside. consider using TARDIS flag.

I see that but as I asked in the discord if that's the case why is that a warning when there are tons of already existing bags that like the bag directly above my new bag fit the same logic but don't draw the error