As the bookkeeping data is spread between three arrays, sorting a
component pool is not trivial and thus not something to duplicate around
the codebase.
As an implementation detail, inserting null hierarchies (src hierarchy
is null) is supported for ease of hierarchy construction from data. No
component data is copied, only the child and parent indices and counts
are updated.
While the libraries are probably getting a little out of hand, the
separation into its own directory is probably a good thing as an ECS
should not be tied to scenes. This should make the ECS more generally
useful.
