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/bithumb/bithumb.go

@@ -3,6 +3,8 @@ package bithumb
 import (
 	"bytes"
 	"context"
+	"encoding/base64"
+	"encoding/hex"
 	"errors"
 	"fmt"
 	"math"
@@ -565,26 +567,21 @@ func (b *Bithumb) SendAuthenticatedHTTPRequest(ctx context.Context, ep exchange.
 	var intermediary json.RawMessage
 	err = b.SendPayload(ctx, request.Auth, func() (*request.Item, error) {
 		// This is time window sensitive
-		tnMS := time.Now().UnixMilli()
-		n := strconv.FormatInt(tnMS, 10)
+		n := strconv.FormatInt(time.Now().UnixMilli(), 10)
 
 		params.Set("endpoint", path)
 
 		payload := params.Encode()
 		hmacPayload := path + string('\x00') + payload + string('\x00') + n
 
-		var hmac []byte
-		hmac, err = crypto.GetHMAC(crypto.HashSHA512,
-			[]byte(hmacPayload),
-			[]byte(creds.Secret))
+		hmac, err := crypto.GetHMAC(crypto.HashSHA512, []byte(hmacPayload), []byte(creds.Secret))
 		if err != nil {
 			return nil, err
 		}
-		hmacStr := crypto.HexEncodeToString(hmac)
 
 		headers := make(map[string]string)
 		headers["Api-Key"] = creds.Key
-		headers["Api-Sign"] = crypto.Base64Encode([]byte(hmacStr))
+		headers["Api-Sign"] = base64.StdEncoding.EncodeToString(([]byte(hex.EncodeToString(hmac))))
 		headers["Api-Nonce"] = n
 		headers["Content-Type"] = "application/x-www-form-urlencoded"
 

exchanges/bithumb/bithumb_ws_orderbook.go

@@ -93,7 +93,7 @@ func (b *Bithumb) applyBufferUpdate(pair currency.Pair) error {
 	}
 
 	if recent != nil {
-		err = b.obm.checkAndProcessUpdate(b.processBooks, pair, recent)
+		err = b.obm.checkAndProcessOrderbookUpdate(b.processBooks, pair, recent)
 		if err != nil {
 			log.Errorf(
 				log.WebsocketMgr,
@@ -351,7 +351,7 @@ func (o *orderbookManager) fetchBookViaREST(pair currency.Pair) error {
 	}
 }
 
-func (o *orderbookManager) checkAndProcessUpdate(processor func(*WsOrderbooks) error, pair currency.Pair, recent *orderbook.Base) error {
+func (o *orderbookManager) checkAndProcessOrderbookUpdate(processor func(*WsOrderbooks) error, pair currency.Pair, recent *orderbook.Base) error {
 	o.Lock()
 	defer o.Unlock()
 	state, ok := o.state[pair.Base][pair.Quote][asset.Spot]