Provide functionality for assessing stake shift for Genesis peer snapshots

[amesgen]

Genesis requires a peer snapshot file for the Network layer to sample big ledger peers in order to satisfy the Honest Availability Assumption.

However, the stake quantities in this peer snapshot file might be stale compared to the current stake distribution ; this staleness can be quantified by the stake shift, see #1421 (comment) for references.

For monitoring purposes (in order to detect big stake shifts, eg due to exchanges), in order to decide when we should provide a new peer snapshot file, we decided to add a cardano-cli command that can compute this stake shift (reading a peer snapshot file, and comparing it to a stake distribution fetched from the node).

Then, this tool can be easily integrated into existing monitoring systems, raising an alarm if the stake shift increases abruptly.

The goal of this ticket is to expose the necessary functionality such that it can be easily exposed as a cardano-cli command downstream.