Standalone TCP for Health Checker

When client-go creates any number of Clients with the same configuration, such as certificates, it reuses the same TCP connection.

This results in the cluster health check interface using the same TCP connection as the resource synchronized informer, which may cause TCP blocking and increased health check latency if a large number of informers are started for the first time. We add a feature gate - HealthCheckerWithStandaloneTCP to allow users to use a standalone tcp for health checks

./clustersynchro-manager --feature-gates=HealthCheckerWithStandaloneTCP=true
desc feature gates default
Use standalone tcp for health checker HealthCheckerWithStandaloneTCP false

Note: When this feature is turned on, the TCP long connections to member clusters will change from 1 to 2. If 1000 clusters are imported, then ClusterSynchro Manager will keep 2000 TCP connections.