exchanges: Refactor time handling and other minor improvements (#1948)

* exchanges: Refactor time handling and other minor improvements

- Updated Kraken wrapper to utilise new time handling methods.
- Simplified Kucoin types by removing unnecessary structures and using direct JSON unmarshalling.
- Improved websocket handling in Kucoin to directly parse candlestick data.
- Modified Lbank types to use the new time representation.
- Adjusted Poloniex wrapper and types to utilise the new time handling.
- Updated Yobit types and wrapper to reflect changes in time representation.
- Introduced DateTime type for better handling of specific time formats.
- Added tests for DateTime unmarshalling to ensure correctness.
- Rid UTC().Unix and UTC().UnixMilli as it's not needed
- Correct Huobi timestamp usage for some endpoints.
- Rid RFC3339 time parsing since Go does that automatically.

* exchanges: Refactor JSON unmarshalling for various types and improve test coverage

* linter: Update error message in TestGetKlines

* refactor: Simplify JSON unmarshalling in MovementHistory and improve test assertions in GetKlines

* refactor: Improve JSON unmarshalling for channel name and clarify comment in wsProcessOpenOrders

* refactor: Update time handling in Huobi types to use types.Time for createdAt fields and relax GetLiquidationOrders test

* refactor: Move wsTicker, wsSpread, wsTrades, and wsCandle types to kraken_types.go for better organistion

* refactor: Add validation for underlying parameter in GetExpirationTime and update tests

exchanges/bitflyer/bitflyer_wrapper.go

@@ -271,11 +271,6 @@ func (b *Bitflyer) GetRecentTrades(ctx context.Context, p currency.Pair, assetTy
 	}
 	resp := make([]trade.Data, len(tradeData))
 	for i := range tradeData {
-		var timestamp time.Time
-		timestamp, err = time.Parse("2006-01-02T15:04:05.999999999", tradeData[i].ExecDate)
-		if err != nil {
-			return nil, err
-		}
 		var side order.Side
 		side, err = order.StringToOrderSide(tradeData[i].Side)
 		if err != nil {
@@ -289,7 +284,7 @@ func (b *Bitflyer) GetRecentTrades(ctx context.Context, p currency.Pair, assetTy
 			Side:         side,
 			Price:        tradeData[i].Price,
 			Amount:       tradeData[i].Size,
-			Timestamp:    timestamp,
+			Timestamp:    tradeData[i].ExecDate.Time(),
 		}
 	}