[Feature] Maintain heartbeat between proxy and broker

### Is Your Feature Request Related to a Problem?

When the cluster traffic is not high or the cluster size is large enough, the proxy and broker only maintain the connection by sending messages or other information. There is a chance that the connection will be established only when sending or consuming. Because the broker will close the idle connection after 120 seconds.

A logic similar to the previous client is needed to send heartbeats regularly.

### Describe the Solution You'd Like

A logic similar to the previous client is needed to send heartbeats regularly.

### Describe Alternatives You've Considered

no

### Additional Context

_No response_

Trace how the proxy and broker establish and maintain connections, then compare it with the previous client's heartbeat logic mentioned in the issue. Define the regular heartbeat behavior and verify that idle connections remain usable without waiting for message or consume traffic.

Written by the indexing model from the issue text.