Send hearbeat during warm reboot freese (#2923) (#2956)

Orchangent send heartbeat during warm-reboot to prevent Orchagent stuck alert.

Why I did it
Orchangent will freese during warm-reboot, then supervisor-proc-exit-listener will generate false alert during warm reboot:
sonic-net/sonic-buildimage#16686

Work item tracking
Microsoft ADO: 25295846
How I did it
Send heartbeat during warm-reboot freeze.

How to verify it
Pass all UT.
Manually verify issue fixed by check syslog.

Author: liuh-80

orchagent/orchdaemon.cpp

@@ -824,7 +824,7 @@ void OrchDaemon::start()
                     flush();
 
                     SWSS_LOG_WARN("Orchagent is frozen for warm restart!");
-                    sleep(UINT_MAX);
+                    freezeAndHeartBeat(UINT_MAX);
                 }
             }
         }
@@ -993,6 +993,19 @@ void OrchDaemon::heartBeat(std::chrono::time_point<std::chrono::high_resolution_
     }
 }
 
+void OrchDaemon::freezeAndHeartBeat(unsigned int duration)
+{
+    while (duration > 0)
+    {
+        // Send heartbeat message to prevent Orchagent stuck alert.
+        auto tend = std::chrono::high_resolution_clock::now();
+        heartBeat(tend);
+
+        duration--;
+        sleep(1);
+    }
+}
+
 FabricOrchDaemon::FabricOrchDaemon(DBConnector *applDb, DBConnector *configDb, DBConnector *stateDb, DBConnector *chassisAppDb) :
     OrchDaemon(applDb, configDb, stateDb, chassisAppDb),
     m_applDb(applDb),

orchagent/orchdaemon.h

@@ -96,6 +96,8 @@ class OrchDaemon
     void flush();
 
     void heartBeat(std::chrono::time_point<std::chrono::high_resolution_clock> tcurrent);
+
+    void freezeAndHeartBeat(unsigned int duration);
 };
 
 class FabricOrchDaemon : public OrchDaemon