Add a check_vault command
It picks a random directory, requests its cooking from swh-web, and waits for it to complete.
First step for T2126.
Depends on swh/infra/ci-cd/swh-jenkins-jobs!40 (closed) for CI to pass
Test Plan
The tests only check that the output conforms to Icinga's API to the best of my understanding of that API.
Migrated from D2453 (view on Phabricator)