Re-raise StorageArgumentException through API calls.
So clients will get a nice exception looking like the original one, instead of generic RemoteApiError.
Depends on !333 (closed), swh-core!123 (closed)
Test Plan
No new test needed, because the current tests are broken by swh-core!123 (closed), and this diff unbreaks them.
Migrated from D2630 (view on Phabricator)