shard sender into multiple task workers by destination hash

rename Destination::Normal variant

tracing instruments

Signed-off-by: Jason Volk <jason@zemos.net>

src/service/sending/data.rs

@@ -246,7 +246,7 @@ fn parse_servercurrentevent(key: &[u8], value: &[u8]) -> Result<(Destination, Se
 		})?;
 
 		(
-			Destination::Normal(ServerName::parse(server).map_err(|_| {
+			Destination::Federation(ServerName::parse(server).map_err(|_| {
 				Error::bad_database("Invalid server string in server_currenttransaction")
 			})?),
 			if value.is_empty() {