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/helpers_test.go

@@ -402,15 +402,10 @@ func TestGetSpecificAvailablePairs(t *testing.T) {
 func TestIsRelatablePairs(t *testing.T) {
 	t.Parallel()
 	CreateTestBot(t)
-	xbtusd, err := currency.NewPairFromStrings("XBT", "USD")
-	if err != nil {
-		t.Fatal(err)
-	}
 
-	btcusd, err := currency.NewPairFromStrings("BTC", "USD")
-	if err != nil {
-		t.Fatal(err)
-	}
+	btcusd := currency.NewBTCUSD()
+	xbtusd := currency.NewPair(currency.XBT, currency.USD)
+	xbtusdt := currency.NewPair(currency.XBT, currency.USDT)
 
 	// Test relational pairs with similar names
 	result := IsRelatablePairs(xbtusd, btcusd, false)
@@ -424,22 +419,12 @@ func TestIsRelatablePairs(t *testing.T) {
 		t.Fatal("Unexpected result")
 	}
 
-	btcusdt, err := currency.NewPairFromStrings("BTC", "USDT")
-	if err != nil {
-		t.Fatal(err)
-	}
-
 	// Test relational pairs with similar names but with Tether support disabled
-	result = IsRelatablePairs(xbtusd, btcusdt, false)
+	result = IsRelatablePairs(xbtusd, currency.NewBTCUSDT(), false)
 	if result {
 		t.Fatal("Unexpected result")
 	}
 
-	xbtusdt, err := currency.NewPairFromStrings("XBT", "USDT")
-	if err != nil {
-		t.Fatal(err)
-	}
-
 	// Test relational pairs with similar names but with Tether support enabled
 	result = IsRelatablePairs(xbtusdt, btcusd, true)
 	if !result {
@@ -505,7 +490,7 @@ func TestIsRelatablePairs(t *testing.T) {
 
 	// Test relationl pairs with similar names, different fiat currencies and
 	// with Tether enabled
-	result = IsRelatablePairs(usdbtc, btcusdt, true)
+	result = IsRelatablePairs(usdbtc, currency.NewBTCUSDT(), true)
 	if !result {
 		t.Fatal("Unexpected result")
 	}