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

engine/rpcserver.go

@@ -2,6 +2,7 @@ package engine
 
 import (
 	"context"
+	"encoding/base64"
 	"errors"
 	"fmt"
 	"net"
@@ -20,7 +21,6 @@ import (
 	"github.com/shopspring/decimal"
 	"github.com/thrasher-corp/gct-ta/indicators"
 	"github.com/thrasher-corp/gocryptotrader/common"
-	"github.com/thrasher-corp/gocryptotrader/common/crypto"
 	"github.com/thrasher-corp/gocryptotrader/common/file"
 	"github.com/thrasher-corp/gocryptotrader/common/file/archive"
 	"github.com/thrasher-corp/gocryptotrader/common/key"
@@ -102,7 +102,7 @@ func (s *RPCServer) authenticateClient(ctx context.Context) (context.Context, er
 		return ctx, errors.New("basic not found in authorization header")
 	}
 
-	decoded, err := crypto.Base64Decode(strings.Split(authStr[0], " ")[1])
+	decoded, err := base64.StdEncoding.DecodeString(strings.Split(authStr[0], " ")[1])
 	if err != nil {
 		return ctx, errors.New("unable to base64 decode authorization header")
 	}