Items & inventory rewrite

[Mooses2k]

ITEMS & INVENTORY

• component approach rather than inheritance; modularize item scenes (remembering savegames & better handling across lvls)
• the root node of the items should do much less and the actual functionality should be implemented as children nodes
• 1 object per glb, instance from glb rather than copy the mesh and embed in the tscn (side note, we have new ammo & candle glbs ready when we do this)
• implement stacks #22
• automatically add mesh_instance.gd to EquipmentItem meshes on import script

• 359

• 169 for things like not having separate smoke particle scenes for each gun

• Rename LargeObjectDropSound to just LargeObject and actually inherit out all large objects from RigidBody