#5313 feat/gate io connector update

GateIO exchance connector refactoring to bring the code to the latest standards. The class ExchangePyBase was modified to serve as the new building base for centralized exchanges connectors. All the generic logic was moved to it and also the methods expected to be implemented by subclasses were created as abstract methods. The following connectors have been modified to be now subclasses of the new base class:

• BInance spot
• Kucoin
• GateIO Proposal of integration_test_tool.py in test/connector to aid manual testing. The script uses real connections with the exchanges and executes basic operations without mocking anything.

PR: https://github.com/hummingbot/hummingbot/pull/5313