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/kline/kline_test.go

@@ -1,7 +1,6 @@
 package kline
 
 import (
-	"fmt"
 	"math/rand"
 	"os"
 	"path/filepath"
@@ -371,10 +370,7 @@ func setupTest(t *testing.T) {
 	t.Helper()
 	if verbose {
 		err := testhelpers.EnableVerboseTestOutput()
-		if err != nil {
-			fmt.Printf("failed to enable verbose test output: %v", err)
-			os.Exit(1)
-		}
+		require.NoError(t, err, "EnableVerboseTestOutput must not error")
 	}
 
 	testhelpers.MigrationDir = filepath.Join("..", "..", "database", "migrations")