FEATURE: [xfundingv2] add option to enable follower TWAP worker and improve notification messages

[dboyliao]

Summary of Changes

• Configurable Follower TWAP Worker: Added UseFollowerTWAPWorkerConfig option to the Strategy struct. When enabled, the follower TWAP worker overrides order type to TWAPOrderTypeTaker; otherwise, it preserves the configured worker settings.
• Interactive Close Round via Slack: Added support for interactive close actions (newInteractiveCloseRound) in notifications when slackEvtID is configured:
  • When a round transitions to the RoundReady state.
  • When a funding rate flip occurs while still within the minimum holding time.
• Refined Alert Messaging & Notification Handling:
  • Softened hedge deviation halt alerts from "Manual intervention is required" to "Might need manual intervention".
  • Cleaned up and consolidated bbgo.Notify format strings across round state transitions (RoundReady, RoundClosing, RoundClosed).