Allow inspecting World for debugging entity issues and other

[djeedai]

What problem does this solve or what need does it fill?

Trying to find why an Entity is not found in the render World by dumping that world with a trace!() just before panic.

What solution would you like?

Allow iterating somehow on entities, components, and archetypes, to allow debugging. Or at least allow dumping the archetypes. Currently only Entities and Components implement Debug, not Archetypes. And entities have no ID, only an EntityLocation that seem to refer to the archetype. So one cannot locate an entity by ID into a world.

What alternative(s) have you considered?

I don't see any. trace!() is already a last-resort technique which dumps in a rather indigestible format; I would have preferred allowing direct read-only iteration (though can understand if that's forbidden for ECS safety reasons).

Additional context

Trying to debug thread 'main' panicked at 'called Result::unwrap()on anErr value: NoSuchEntity',. I know the entity ID, but cannot see if it's in the world, or what other entities are there that would guide my debugging.

[alice-i-cecile]

Related to #1467 and #1130.