Deploy loader.metadata credentials for high and oneshot loaders

As well.

Otherwise, they get rate limited when triggering their loading. That might be arguably fine for oneshot loaders which are only helping other workers with the ingestions.

It's not fine for the high priority loaders which are expected to answer fast (save code now).

May 13 14:44:30 worker18 python3[1693713]: [2022-05-13 14:44:30,970: INFO/ForkPoolWorker-207] Rate limits exhausted for all tokens. Sleeping for 3398.029220 seconds.
May 13 14:45:21 worker18 python3[1692790]: [2022-05-13 14:45:21,137: INFO/ForkPoolWorker-197] Task swh.loader.git.tasks.UpdateGitRepository[41f1e5de-9994-43a8-88c0-1b2086b9ab76] succeeded in 239.5409866529517s: {'status': 'eventful'}
May 13 14:45:25 worker18 python3[1673353]: [2022-05-13 14:45:25,895: INFO/MainProcess] Received task: swh.loader.git.tasks.UpdateGitRepository[c6789ee1-dc72-4c55-86a9-774f7b8d8c2e]
May 13 14:45:26 worker18 python3[1694168]: [2022-05-13 14:45:26,057: INFO/ForkPoolWorker-208] Load origin 'https://github.com/nboute/fractol_new' with type 'git'
May 13 14:45:26 worker18 python3[1694168]: [2022-05-13 14:45:26,124: WARNING/ForkPoolWorker-208] No tokens set in configuration, using anonymous mode
May 13 14:45:26 worker18 python3[1694168]: [2022-05-13 14:45:26,274: INFO/ForkPoolWorker-208] Rate limits exhausted for all tokens. Sleeping for 3343.725802 seconds.

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Migrated from T4243 (view on Phabricator)