Populate the visit status value in save code now request

Related to #3266 (closed) Depends on !537 (closed)

Test Plan

tox

happy tests are still happy

container: db row after a save code now have their visit_status populated

swh-web=# select * from save_origin_request order by request_date desc;
 id |         request_date          | visit_type |                           origin_url                           |  status  | loading_task_id |          visit_date           | loading_task_status | visit_status
----+-------------------------------+------------+----------------------------------------------------------------+----------+-----------------+-------------------------------+---------------------+--------------
  9 | 2021-04-21 12:03:52.083365+00 | git        | https://github.com/WerWolv/ImHex                               | accepted |              18 |                               | running             |
  8 | 2021-04-21 11:57:40.967667+00 | git        | https://github.com/divnix/devos                                | accepted |              16 | 2021-04-21 11:58:34.487761+00 | succeeded           | full
  7 | 2021-04-21 11:32:02.161929+00 | git        | https://github.com/org-trello/org-trello                       | accepted |              14 | 2021-04-21 11:34:02.994894+00 | succeeded           | full

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Migrated from D5569 (view on Phabricator)