Investigate timeout issues when querying snapshot data

Last Friday, timeout issues were reported by the web application in production related to the retrieval of snapshot data from the archive:

• https://sentry.softwareheritage.org/organizations/swh/issues/4185/?project=13&query=is%3Aunresolved&statsPeriod=14d
• https://sentry.softwareheritage.org/organizations/swh/issues/4184/events/?project=3

As a consequence, the archive could not be browsed in a snapshot context anymore as an error 500 was raised in that case.

This calls for an investigation of these timeout issues to avoid hitting such denial of service again in production.

---

Migrated from T2734 (view on Phabricator)