model: Rename OriginVisitUpdate to OriginVisitStatus

This also adapts the hypothesis strategies, using the plural form origin_visit_statuses. That plural form is acceptable because in our context, the statuses are countable.

Related to T2310 Related to [1]

To be able to update names in the current swh-storage!919 (closed) swh-storage!920 (closed) swh-storage!921 (closed) (they use origin visit update).

• [1] https://hebdo.framapad.org/p/9g09-0jjinnno5y?lang=en

Test Plan

tox

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Migrated from D3001 (view on Phabricator)