Activate saved origin browse link only when loading data are available in database

Currently in the Save Code Now Web UI, the link to browse an origin requested to be saved is activated based on the status of the associated celery task that executed the loading.

However, it does not necessarily mean that the loading data are available in the storage database used by the webapp to query archive data (especially when using the replica database which can have some lags with the primary database).

We should activate the origin browse link only when the loading data are available in database by checking the visit status value. When it is not yet available, we should add a tooltip on the origin URL in the Save Code Now requests table indicating that the loading succeeded but data were not yet written to database.

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Migrated from T3848 (view on Phabricator)