This also opens an "order" parameter to the "origin-visit-get" storage endpoint to
allow the search on snapshot-get-latest/origin-get-latest* function to be consistent.
If we limit the search, we must start from the most recent visits (so order
"visit-id desc"). Otherwise, at some point (passed the limit), we will never be
able to find what we look for.
This also explicits the current order on the visit id for the endpoint
"origin-visit-get" which is "visit-id asc" (currently implicit within the
respective backends).
Depends on D3349
As a means to solve timeouts when querying last visit [1]
[1] https://sentry.softwareheritage.org/share/issue/3786bfd7b0414464a037d6a2a6c6ff68/