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/btse/btse.go

@@ -3,6 +3,7 @@ package btse
 import (
 	"bytes"
 	"context"
+	"encoding/hex"
 	"errors"
 	"io"
 	"net/http"
@@ -516,7 +517,7 @@ func (b *BTSE) SendAuthenticatedHTTPRequest(ctx context.Context, ep exchange.URL
 				host += "?" + values.Encode()
 			}
 		}
-		headers["btse-sign"] = crypto.HexEncodeToString(hmac)
+		headers["btse-sign"] = hex.EncodeToString(hmac)
 
 		return &request.Item{
 			Method:        method,

exchanges/btse/btse_websocket.go

@@ -2,6 +2,7 @@ package btse
 
 import (
 	"context"
+	"encoding/hex"
 	"errors"
 	"net/http"
 	"strconv"
@@ -76,18 +77,14 @@ func (b *BTSE) WsAuthenticate(ctx context.Context) error {
 	nonce := strconv.FormatInt(time.Now().UnixMilli(), 10)
 	path := "/ws/spot" + nonce
 
-	hmac, err := crypto.GetHMAC(crypto.HashSHA512_384,
-		[]byte((path)),
-		[]byte(creds.Secret),
-	)
+	hmac, err := crypto.GetHMAC(crypto.HashSHA512_384, []byte((path)), []byte(creds.Secret))
 	if err != nil {
 		return err
 	}
 
-	sign := crypto.HexEncodeToString(hmac)
 	req := wsSub{
 		Operation: "authKeyExpires",
-		Arguments: []string{creds.Key, nonce, sign},
+		Arguments: []string{creds.Key, nonce, hex.EncodeToString(hmac)},
 	}
 	return b.Websocket.Conn.SendJSONMessage(ctx, request.Unset, req)
 }