algos.origin: Open origin-get-latest-visit-status function

This will allow to avoid repeating the same pattern of retrieving the last visit status for a given origin.

(Allowing to simplify in the process swh-indexer!449 (closed) swh-loader-core!382 (closed) swh-loader-git!125 (closed) swh-loader-mercurial!106 (closed) swh-loader-svn!172 (closed)...)

Note: I also splitted the tests per filter types (type, status, snapshot) for a better readability [1]

• [1] !426 (closed)#inline-22849

Related to T2310

Test Plan

tox

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Migrated from D3313 (view on Phabricator)