chore: cli wallet-status outputs pretty json

Changes `neptune-cli wallet-status` to pretty-print json instead of
using wallet_status.to_string(), ie impl Display.

This change is motivated by the block explorer, which instructs users
to obiain utxo-index from output of wallet-status, but previously the
field was unlabelled and the output was badly formatted mostly without
newlines, making it quite human unfriendly.

With this change:
 + the utxo index is labelled as: aocl_leaf_index
 + digests are nicely hex formatted instead of BFieldElement list.
 + the output is nicely formatted and human readable
 + the output is also machine readable

src/bin/neptune-cli.rs

@@ -358,7 +358,7 @@ async fn main() -> Result<()> {
         }
         Command::WalletStatus => {
             let wallet_status: WalletStatus = client.wallet_status(ctx).await?;
-            println!("{}", wallet_status)
+            println!("{}", serde_json::to_string_pretty(&wallet_status)?);
         }
         Command::OwnReceivingAddress => {
             let rec_addr: generation_address::ReceivingAddress =