Deprecate and remove insert_or_spawn_batch

[alice-i-cecile]

Just like in #15459 / #15652 for get_or_spawn, insert_or_spawn_batch is an anti-pattern: it uses entity IDs in a non-opaque way, attempting to assign specific meaning to certain entities. With the retained rendering world in place, we should remove it to discourage this pattern and enforce the ECS invariants more strongly.

#15702 should be merged first, to ensure that the migration path for the non-footgunny part of this API is smooth.

[alice-i-cecile]

#18054 showcases a serious performance footgun involved with these methods.