[sync] Improve sync

Make every request in batch, to save round trip times
Fetch timestamp of blockheader to populate timestamp field in transaction
Remove listunspent requests because we can compute it from our history

src/blockchain/mod.rs

@@ -40,6 +40,7 @@ use crate::database::BatchDatabase;
 use crate::error::Error;
 use crate::FeeRate;
 
+#[cfg(any(feature = "electrum", feature = "esplora"))]
 pub(crate) mod utils;
 
 #[cfg(any(feature = "electrum", feature = "esplora", feature = "compact_filters"))]