(poc): Add Event Recording in Dry Run Flow to Improve XCM Debugging

[raymondkfcheung]

This PR enhances the XCM dry-run flow by introducing a new storage item to capture emitted events, improving observability during testing and debugging.

Key Changes

• Added a new EmittedEvent storage to record emitted events during dry-run execution.
• Ensured events are recorded before post_process to capture intermediate state changes.
• Integrated event recording in execute_xcm_transfer to persist emitted events for debugging.
• Verified that recorded events are still available after post_process.

Findings

• Emitted events were not retained after post_process in the original dry-run flow.
• With the new storage, events are now correctly recorded before post_process, ensuring they are captured during XCM execution failures or intermediate steps.