This supersedes #17503, given the per-connection state is being heavily
rewritten it felt easier to recreate the PR on top of that work.
This correctly handles the case of timeline limits going up and down.
This does not handle changes in `required_state`, but that can be done
as a separate PR.
Based on #17575.
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Co-authored-by: Eric Eastwood <eric.eastwood@beta.gouv.fr>
