MES - Moog's End Structures

Added

• Converted to datapack with dependency on MoogsStructureLib (moogs_structures)
• New loot tables for empty barrels: a minimal end-themed junk table and a rarer mid-tier variant
• All empty containers now have loot tables assigned

Fixed

• All custom type IDs updated to use the correct moogs_structures namespace
• Replaced all vanilla end city treasure references with a custom equivalent
• Fixed sign NBT format incompatible with 1.20
• Removed broken entry from Mega Ship Crashed Deepslate's top pool
• Removed 5 unused processor lists