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/bitmex/bitmex_websocket.go

@@ -2,6 +2,7 @@ package bitmex
 
 import (
 	"context"
+	"encoding/hex"
 	"errors"
 	"fmt"
 	"net/http"
@@ -577,17 +578,17 @@ func (b *Bitmex) websocketSendAuth(ctx context.Context) error {
 	if err != nil {
 		return err
 	}
+
 	timestamp := time.Now().Add(time.Hour * 1).Unix()
 	timestampStr := strconv.FormatInt(timestamp, 10)
 	hmac, err := crypto.GetHMAC(crypto.HashSHA256, []byte("GET/realtime"+timestampStr), []byte(creds.Secret))
 	if err != nil {
 		return err
 	}
-	signature := crypto.HexEncodeToString(hmac)
 
 	req := WebsocketRequest{
 		Command:   "authKeyExpires",
-		Arguments: []any{creds.Key, timestamp, signature},
+		Arguments: []any{creds.Key, timestamp, hex.EncodeToString(hmac)},
 	}
 
 	resp, err := b.Websocket.Conn.SendMessageReturnResponse(ctx, request.Unset, req.Command, req)