Remote Vault

[davide-baldo]

Note

This PR is merging toward davide-baldo/kafka-multiple-consumers rather than develop, but i'll be merged to develop without a second review (unless heavy rebase was needed)

This PR implements the concept of remote vault.
A remote vault is accessing a vault configured in another Ockam Node. This is to allow setting up a shared vault without the need to introduce an external service, which comes really handy for demos and simple setups.
All APIs current supported by Vault are exposed and working, but the secure channel APIs are impractical due to latency and are meant mostly for testing and sketching up a new use case rather than production use.

The remote vault communication happens using a pre-determined identity, authority, and vault. These parameters were serialized inside the database, so we don't need to specify it again every time a remote vault might be used (almost every single command). The remote vault adopts a basic live check, a ping every 10 seconds before usage, if it times out it'll re-connect.

To allow using multiple identities from within the same node, the first commit is about moving the necessary concepts from the node manager to a new ConnectionInstantiator, which holds all the necessary information and traits.

Also, the usage of the log crate was fully removed in favor of trace, to produce a more readable, easier to debug log.