This commit enhances the /profit Telegram command to allow filtering by trade direction.
- The `_profit` handler in `telegram.py` now parses 'long'/'short' arguments and passes the direction to the RPC layer.
- The `_rpc_trade_statistics` method in `rpc.py` is updated to filter trades based on the provided direction. It has also been refactored for lower complexity.
- The `/help` command documentation is updated to reflect the new functionality.
- Corresponding unit tests in `test_rpc_telegram.py` are updated and extended to cover the new cases.
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