codebase: Cleanup various things (#1935)

* codebase: Rid base64/hex to string common funcs

* codebase: Rid local scope variable usage and other improvements

* codebase: Refactor currency pair usage across multiple exchanges

- Updated HitBTC tests to use the new currency pair format.
- Modified Kraken futures types to use currency.Pair instead of string for Symbol.
- Adjusted Kraken wrapper methods to handle currency pairs correctly.
- Refined OKX tests and types to utilize currency.Pair for instrument IDs.
- Enhanced Poloniex tests to consistently use predefined currency pairs.
- Streamlined order and orderbook tests to replace string pairs with currency.NewBTCUSD().
- Improved Yobit tests to utilize a standardized currency pair format.
- Updated validator wrapper to use currency pairs directly instead of string conversions.

* codebase: Use types.Number where possible

* refactor: update PayoutFee type to types.Number for consistency

* Refactor: Remove crypto functions to use standard library and other minor changes

- Removed custom crypto functions for SHA256, SHA512, and MD5 from the common/crypto package.
- Replaced usages of removed functions with standard library implementations in various files including:
  - cmd/websocket_client/main.go
  - engine/apiserver.go
  - exchanges/kraken/kraken.go
  - exchanges/lbank/lbank.go
  - exchanges/okx/okx_business_websocket.go
  - exchanges/kucoin/kucoin_websocket.go
  - gctscript/vm/vm.go
- Updated tests to reflect changes in the crypto functions.
- Renamed several functions for clarity, particularly in the context of order book updates across multiple exchanges.

* refactor: replace assert with require for consistency in test assertions

* refactor: Improve Binance futures candlestick test, standardise orderbook update function names and improve test parallelism

* refactor: Replace require.Len with require.Equal for better output in TestGetFuturesKlineData

exchanges/trade/trade_test.go

@@ -37,12 +37,11 @@ func TestAddTradesToBuffer(t *testing.T) {
 	if err != nil {
 		t.Error(err)
 	}
-	cp, _ := currency.NewPairFromString("BTC-USD")
 	err = AddTradesToBuffer([]Data{
 		{
 			Timestamp:    time.Now(),
 			Exchange:     "test!",
-			CurrencyPair: cp,
+			CurrencyPair: currency.NewBTCUSD(),
 			AssetType:    asset.Spot,
 			Price:        1337,
 			Amount:       1337,
@@ -60,7 +59,7 @@ func TestAddTradesToBuffer(t *testing.T) {
 		{
 			Timestamp:    time.Now(),
 			Exchange:     "test!",
-			CurrencyPair: cp,
+			CurrencyPair: currency.NewBTCUSD(),
 			AssetType:    asset.Spot,
 			Price:        0,
 			Amount:       0,
@@ -78,7 +77,7 @@ func TestAddTradesToBuffer(t *testing.T) {
 		{
 			Timestamp:    time.Now(),
 			Exchange:     "test!",
-			CurrencyPair: cp,
+			CurrencyPair: currency.NewBTCUSD(),
 			AssetType:    asset.Spot,
 			Price:        -1,
 			Amount:       -1,
@@ -156,7 +155,7 @@ func TestTradeToSQLData(t *testing.T) {
 
 func TestConvertTradesToCandles(t *testing.T) {
 	t.Parallel()
-	cp, _ := currency.NewPairFromString("BTC-USD")
+	cp := currency.NewBTCUSD()
 	startDate := time.Date(2020, 1, 1, 1, 0, 0, 0, time.UTC)
 	candles, err := ConvertTradesToCandles(kline.FifteenSecond, []Data{
 		{