Add user-facing events for applying updates after syncing

[tnull]

Describe the enhancement
When syncing, Wallet::apply_update returns Result<(), CannotConnectError> which doesn't give any information if/how all of the changes have been applied. It would be great to return a list of human readable events that reflect how the Wallet funds/status changed (e.g., with Inbound/Outbound variants).

Use case
Notifying the user about relevant on-chain events (e.g., "payment received"/"payment sent").