Fix: New entity container struct

[IsaacMcCracken]

Make a new container struct for entities for the world struct instead of using entity list

typedef struct Entities Entities;
struct Entities {
  Entity *first;
  Entity *last;
  U64 count;
  Entity **grid; // for quick look up
  Arena *arena; // allocator just for arenas
  Entity *free_list; // pool allocator stuff to reuse memory
}

[IsaacMcCracken]

@IsaacMcCracken was pog and closed this thanks to him the suffering will end