Refactor the Rpc support

[etorreborre]

The ockam_command crate contains some support to make RPC calls to a node. However this RPC support is also used to make local calls to a NodeManager.

The purpose of this story is to remove the Embedded mode from the Rpc struct so that local calls are made directly.
At the minimum this supposes to:

• remove the integrating printing of response from the Rpc client
• simplify the Rpc API and directly return typed values when possible (at the moment, the Rpc API exposes too many details about the processing of a response)
• possibly revisit the necessity of a RpcBuilder (Maybe merge it within the Rpc struct)
• simplify the creation of a Rpc into 2 distinct cases: "embedded" and "background"
• make specific RPC clients for accessing: the controller, the project node, the authority node
• create typed interfaces for each of those clients depending on their capabilities (for example the Controller can manage projects)
  • Projects
  • Spaces
  • Subscriptions
  • Invitations
  • Enrollment
• use the typed interfaces everywhere possible
• remove unused code using the old RpcClient
• fix the examples involving credentials
• fix the support for creating tickets in one case
• simplify the relationship between NodeManagerWorker and NodeManager (all the logic should be in the NodeManager)
• put back the Connection support for creating secure channels
• pass the unit tests
• pass the local bats tests
• document and comment
• pass the Orchestrator bats tests