Automatically disconnect and remove the peer from consul registry

[anhthii]

Automatically disconnect and remove unresponsive peers from Consul registry

Description

This PR enhances peer health management in the MPC node registry to ensure disconnected or unresponsive peers are automatically removed from Consul.

Key Changes

registry

• Added healthCheck using DirectMessaging to actively probe peers via NATS.
• Implemented checkPeersHealth routine that periodically sends health check messages to all ready peers.
• If a peer does not respond (detected by "no responders" error), its ready key is deleted from Consul.
• Updated NewRegistry to accept directMessaging for health checks.

point2point

• Added SendToOtherWithRetry method with configurable retry attempts, delays, and backoff for reliable health checks.
• Improved Listen method to handle subscription flush errors and clean up on failure.

main.go

• Updated NewRegistry initialization to pass in directMessaging.
• Added NATS Drain() call during shutdown for clean disconnection.

keygen_consumer

• Fixed log messages to correctly reference keygen events instead of signing events.

Impact

• Ensures the registry always reflects the actual set of active peers.
• Reduces stale peer entries in Consul, preventing potential coordination or signing errors.
• Improves node reliability and self-healing in multi-peer setups.