Deploy vault "git bare" tarball cooker (swh-vault v0.6)

This requires:

• the swh.vault v0.6
• some changes in the default configuration [1] so the vault benefits from using objstorage and graph [2] services.

First staging then production if everything is ok.

• [1] migrated/migration$1071

• [2] The graph service is not ready for prime time, it needs some packaging and internal reworking regarding the existing swh.graph.client module (possibly to be moved to swh.web.client)

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Migrated from T3412 (view on Phabricator)