reconnect() holds the pool slot while sleeping between attempts

`Session::reconnect()` sleeps `retry_interval` between passes and walks all endpoints while still holding its pool slot. With defaults (3 endpoints, 3 attempts, 1s interval) the worst case is ~92s, during which concurrent `acquire()` callers get "pool exhausted" — an error that points away from the real cause.

Fix: when the session is handed out from a pool, skip the between-attempt sleeps (the slot is still held, but the hold time drops to the connect+handshake attempts), or shorten them. Standalone sessions keep the current C#-style pacing.

Empieza leyendo Session::reconnect y la ruta del pool que entrega las sesiones a los llamadores de acquire, centrándote en cómo se identifican las sesiones pooled frente a las standalone. Verifica que los intentos de reconnect pooled no conserven las pausas entre intentos, mientras que las sesiones standalone mantengan su ritmo actual, y confirma que la adquisición concurrente del pool ya no falle debido al retraso.

Escrito por el modelo de indexación a partir del texto del issue.