Optimize component operations

[mlange-42]

Component operations like adding and removing, and particularly creating entities, are still slower than in Arche (≈30%).

Identify the additional cost and try to optimize it. Initial guesses:

• Preparing relations incurs a cost that could be optimized.
• The archetype graph may be slower, maybe because of the use of slice indices instead of pointers.

There must still be something else, that particularly affects entity creation.