Export privacy settings as enums not types

[lmeyerov]

Client users manipulating security settings can pass in private / organization / etc, but for type safety, cleaner if they can use an exported mode enum. Currently we only expose mode as a type.

See also internal dogfooding discussion: https://github.com/graphistry/graphistry/pull/1910#discussion_r1159384204

This is probably better as a breaking change to avoid confusing redundancy