Give fast feedback on long operations

[nymius]

Describe the enhancement
Some wallet operations seem to hang up, even if they are working as intended. It would be nice to ensure all commands show liveness thorough their execution.

I found the Doherty Threshold, and I think it express succinctly what I'm referring to here.

Use case
Let users know the cli is making progress for operations like full scanning or synchronization.

[tvpeter]

Can you specify which subcommands you think should output their progress during execution? The full_scan subcommand does print progress in the terminal.

[nymius]

full_scan for example, it has output, but it is slow to arrive, at least the first line.

[zealsham]

@tvpeter would love to work on this as an intro to bdk-cli for me. @nymius added a simple println! "starting full_scan ....." before any of the feature flags body in the full_scan command and it seems to provide the visual feedback