Adapt storage.revision_get calls according to latest api change

This also allows the new extra_headers conversion. (current revisions might not have it yet but at some point, they will eventually get migrated to this [1] ;)

That may also fix the master build now (some new code got pushed in the repository since the new storage 0.14.0 release) [2]

• [1] swh/infra/sysadm-environment#2564

• [2] https://jenkins.softwareheritage.org/job/DWAPPS/job/tests/1631/console

Related to T645

Test Plan

tox (failing until release storage > 0.13.3)

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Migrated from D3877 (view on Phabricator)