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.go

@@ -2,6 +2,7 @@ package bitmex
 
 import (
 	"context"
+	"encoding/hex"
 	"errors"
 	"fmt"
 	"net/http"
@@ -883,39 +884,31 @@ func (b *Bitmex) SendAuthenticatedHTTPRequest(ctx context.Context, ep exchange.U
 
 	var respCheck any
 	newRequest := func() (*request.Item, error) {
-		expires := time.Now().Add(time.Second * 10)
-		timestamp := expires.UnixNano()
-		timestampStr := strconv.FormatInt(timestamp, 10)
-		timestampNew := timestampStr[:13]
+		ts := strconv.FormatInt(time.Now().Add(time.Second*10).UnixMilli(), 10)
 
 		headers := make(map[string]string)
 		headers["Content-Type"] = "application/json"
-		headers["api-expires"] = timestampNew
+		headers["api-expires"] = ts
 		headers["api-key"] = creds.Key
 
 		var payload string
 		if params != nil {
-			err = params.VerifyData()
-			if err != nil {
+			if err := params.VerifyData(); err != nil {
 				return nil, err
 			}
-			var data []byte
-			data, err = json.Marshal(params)
+			data, err := json.Marshal(params)
 			if err != nil {
 				return nil, err
 			}
 			payload = string(data)
 		}
 
-		var hmac []byte
-		hmac, err = crypto.GetHMAC(crypto.HashSHA256,
-			[]byte(verb+"/api/v1"+path+timestampNew+payload),
-			[]byte(creds.Secret))
+		hmac, err := crypto.GetHMAC(crypto.HashSHA256, []byte(verb+"/api/v1"+path+ts+payload), []byte(creds.Secret))
 		if err != nil {
 			return nil, err
 		}
 
-		headers["api-signature"] = crypto.HexEncodeToString(hmac)
+		headers["api-signature"] = hex.EncodeToString(hmac)
 
 		return &request.Item{
 			Method:        verb,

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)