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/credentials.go

@@ -2,12 +2,12 @@ package exchange
 
 import (
 	"context"
+	"encoding/base64"
 	"errors"
 	"fmt"
 	"strings"
 
 	"github.com/thrasher-corp/gocryptotrader/common"
-	"github.com/thrasher-corp/gocryptotrader/common/crypto"
 	"github.com/thrasher-corp/gocryptotrader/config"
 	"github.com/thrasher-corp/gocryptotrader/exchanges/account"
 	"github.com/thrasher-corp/gocryptotrader/log"
@@ -168,7 +168,7 @@ func (b *Base) VerifyAPICredentials(creds *account.Credentials) error {
 	}
 
 	if b.API.CredentialsValidator.RequiresBase64DecodeSecret && !creds.SecretBase64Decoded {
-		decodedResult, err := crypto.Base64Decode(creds.Secret)
+		decodedResult, err := base64.StdEncoding.DecodeString(creds.Secret)
 		if err != nil {
 			return fmt.Errorf("%s API secret %w: %s", b.Name, errBase64DecodeFailure, err)
 		}
@@ -190,7 +190,7 @@ func (b *Base) SetCredentials(apiKey, apiSecret, clientID, subaccount, pemKey, o
 	b.API.credentials.OneTimePassword = oneTimePassword
 
 	if b.API.CredentialsValidator.RequiresBase64DecodeSecret {
-		result, err := crypto.Base64Decode(apiSecret)
+		result, err := base64.StdEncoding.DecodeString(apiSecret)
 		if err != nil {
 			b.API.AuthenticatedSupport = false
 			b.API.AuthenticatedWebsocketSupport = false