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/order_manager_test.go

@@ -935,7 +935,7 @@ func TestGetOrdersFiltered(t *testing.T) {
 	}
 }
 
-func Test_getFilteredOrders(t *testing.T) {
+func TestGetFilteredOrders(t *testing.T) {
 	m := OrdersSetup(t)
 
 	_, err := m.orderStore.getFilteredOrders(nil)
@@ -1014,7 +1014,7 @@ func TestGetOrdersActive(t *testing.T) {
 	}
 }
 
-func Test_processMatchingOrders(t *testing.T) {
+func TestProcessMatchingOrders(t *testing.T) {
 	m := OrdersSetup(t)
 	exch, err := m.orderStore.exchangeManager.GetExchangeByName(testExchange)
 	if err != nil {
@@ -1094,7 +1094,7 @@ func TestFetchAndUpdateExchangeOrder(t *testing.T) {
 	}
 }
 
-func Test_getActiveOrders(t *testing.T) {
+func TestGetActiveOrders(t *testing.T) {
 	m := OrdersSetup(t)
 	var err error
 	orders := []order.Detail{