Empty structs / Tag components should not consume any memory about arch HOT 1 CLOSED

Problem

This is actually a bit harder to solve, since it would require a totally different handling of certain API calls or a lot of different conditions to make sure a user does not "Set" or "Get" a tag component.

Different solution

Instead a different solution was picked, each tag component still allocates an array ( which still is very very cheap ), but those arrays are not part of the chunk size calculation. This way Transform, Rotation, AITag and Transform, Rotation will fit the same amount of entities into each chunk, regardless of the tag. Since the tag is not being acessed in queries, the speed is also optimal.

This solution is like the golden middle.

Partially solved in b56ec46

from arch.