Key-less datamodel 1: scrap InstanceKey from public logging APIs

[teh-cmc]

This just removes InstanceKeys from the archetypes where they were exposed, and updates all tests/examples/APIs/etc accordingly.

Nothing else changes. Internally, everything is still driven by autogenerated instance keys.

The num_instances field and the associated log-time check ("0, 1, or N?") are still there.

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Part of a series of PR to migrate to a key-less, PoV-less, component-based (as opposed to archetype-based) query model:

• Key-less datamodel 1: scrap InstanceKey from public logging APIs #5395

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[Wumpf]

no turning back now, let's do this!