OrderSend retries and circuit breaker in MQL5

The brief

MQL5 developers face challenges in volatile markets due to unclassified retries and lack of cumulative failure control in Expert Advisors (EAs). This issue is characterized by problems such as requotes, connection drops, and partial fills. To address this, a CRetryExecutor with exponential backoff and explicit error classification has been introduced. Additionally, a CCircuitBreaker with a three-state mechanism is implemented to manage cumulative failures. These solutions aim to improve the reliability and robustness of EAs in MQL5.