Get rid of duplicated Reva config struct

Consolidate all services to use the Reva config struct for the shared package.
This works because all services (except 'notifications', 'thumbnails' and
'webdav') where using the same config keys and environment variables for
setting the reva gateway.
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Internal Server Error - Gitea: Git with a cup of tea
500 Internal Server Error

Gitea Version: 1.28.0+dev-477-g8b6ad49a5f