Remove allocation when adding and removing components

[Anders429]

Currently, adding or removing components requires moving the components from one archetype to another, which requires an allocation here: https://github.com/Anders429/brood/blob/master/src/archetype/mod.rs#L461

Since the components are canonically ordered, this can be optimized away. Rather than popping into a buffer, we can just use the component columns from both archetypes, copying directly from the one into the other.

This is somewhat related to #220.