Split GSS.Registry into authorization and process management layers

[Voronchuk]

Currently all spreadsheet process and Goth auth token are tracked by GSS.Registry module.

Put spreadsheet process tracking into a separate Elixir native Registry instance.

Scope out GSS.Auth module from a current GSS.Registry which will manage Goth auth token: headers = %{"Authorization" => "Bearer #{GSS.Auth.token}"} instead of headers = %{"Authorization" => "Bearer #{GSS.Registry.token}"}