fix(electrum)!: Remove seen_at param from into_tx_graph

and `into_confirmation_time_tx_graph`, since now it makes
sense to use `TxGraph::update_last_seen_unconfirmed`.

Also, use `update_last_seen_unconfirmed` in examples for
electrum/esplora. We show how to update the last seen
time for transactions by calling `update_last_seen_unconfirmed`
on the graph update returned from a blockchain source, passing
in the current time, before applying it to another `TxGraph`.

example-crates/example_electrum/src/main.rs

@@ -299,12 +299,12 @@ fn main() -> anyhow::Result<()> {
         relevant_txids.missing_full_txs(graph.graph())
     };
 
+    let mut graph_update = relevant_txids.into_tx_graph(&client, missing_txids)?;
     let now = std::time::UNIX_EPOCH
         .elapsed()
         .expect("must get time")
         .as_secs();
-
-    let graph_update = relevant_txids.into_tx_graph(&client, Some(now), missing_txids)?;
+    let _ = graph_update.update_last_seen_unconfirmed(now);
 
     let db_changeset = {
         let mut chain = chain.lock().unwrap();