Fixed ImportError due to circular dependency

[losingle]

• Removed the problematic import statement from hummingbot/core/utils/estimate_fee.py that was importing TradeFeeSchemaLoader from hummingbot.client.config.trade_fee_schema_loader.
• This change resolves the ImportError that occurred due to a circular import when initializing Hummingbot.
• Code in estimate_fee.py was refactored to avoid relying on the direct import, ensuring proper module initialization without import loops.

With this fix, the codebase should no longer encounter the ImportError during runtime, thus maintaining the smooth operation of Hummingbot's initialization process.