Kucoin: Change default websocket subscription channel for tickers and orderbooks (#1371)

* kucoin: quick batching support for ticker/trades and orderbooks

* fix test

* kucoin: move pieces add commentry

* kucoin: optimise listOfAssetsCurrencyPairEnabledFor and refactor implementations, address specific orderbook channel subscription handling

* glorious: nits

* thx @thrasher-: nits addressed

* rm types and tests that are not needed

* rm subs checking code, and convert to types.Number

* not needed anymore

* fix tests

* set up reader routine to process updates before init a potential slow websocket subscriber

* implement glorious suggestion

* glorious: nitters

---------

Co-authored-by: Ryan O'Hara-Reid <ryan.oharareid@thrasher.io>

exchanges/gateio/gateio_wrapper.go

@@ -516,9 +516,6 @@ func (g *Gateio) FetchTradablePairs(ctx context.Context, a asset.Item) (currency
 					return nil, err
 				}
 				cp.Quote = currency.NewCode(strings.ReplaceAll(cp.Quote.String(), currency.UnderscoreDelimiter, currency.DashDelimiter))
-				if err != nil {
-					return nil, err
-				}
 				pairs = append(pairs, cp)
 			}
 		}