Refactor: ccxt config is duplicated across exchange subclasses

Refactor: ccxt config is duplicated across exchange subclasses: a task in MiMo-V2.6-RL-harbor-code: MiMo-V2.6-RL Code (Harbor) (Harbor dataset). While working on the leverage / trading-mode code I noticed that several exchange subclasses ( Binance , Gateio , Okex , …) all override ccxt config with…

The task

While working on the leverage / trading-mode code I noticed that several exchange subclasses (`Binance`, `Gateio`, `Okex`, …) all override `_ccxt_config` with essentially the same body:

Part of FineEnvs/MiMo-V2.6-RL-harbor-code.