refactor: clean up the logs and reduce noise

- Remove "Detected Autocrypt-mime message" logs printed for every incoming Autocrypt message.
- Print only a single line at the beginning of receive_imf with both the Message-ID and seen flag.
- Print Securejoin step only once, inside handle_securejoin_handshake or observe_securejoin_on_other_device.
- Do not log "Not creating ad-hoc group" every time ad-hoc group is not created, log when it is created instead.
- Log ID of the chat where Autocrypt-Gossip for all members is received.
- Do not print "Secure-join requested." for {vg,vc}-request, we already log the step.
- Remove ">>>>>>>>>>>>>>>>>>>>>>>>>" noise from securejoin logs.

src/contact.rs

@@ -772,7 +772,7 @@ impl Contact {
 
                 sth_modified = Modifier::Created;
                 row_id = u32::try_from(transaction.last_insert_rowid())?;
-                info!(context, "added contact id={} addr={}", row_id, &addr);
+                info!(context, "Added contact id={row_id} addr={addr}.");
             }
             Ok(row_id)
         }).await?;