[docker-gbsyncd-vs] Run new gbsyncdmgrd in lieu of deprecated gbsyncd_startup.py (sonic-net#7154)

To improve management of docker-gbsyncd-vs. gbsyncd_startup.py simply spawned syncd processes and then exited. In that case, supervisord would no longer manage any processes in the container, and thus there was no way to know if a critical process had exited.

I recently created gbsyncdmgrd to be a more complete, robust replacement for gbsyncd_startup.py.

NOTE: This PR is dependent on the inclusion of gbsyncdmgrd in the sonic-sairedis repo. A submodule update is pending at
sonic-net#7089

Author: jleveque

platform/vs/docker-gbsyncd-vs/critical_processes

@@ -1 +1 @@
-program:syncd
+program:gbsyncdmgrd

platform/vs/docker-gbsyncd-vs/supervisord.conf

@@ -37,8 +37,8 @@ stderr_logfile=syslog
 dependent_startup=true
 dependent_startup_wait_for=rsyslogd:running
 
-[program:syncd]
-command=/usr/bin/gbsyncd_startup.py
+[program:gbsyncdmgrd]
+command=/usr/bin/gbsyncdmgrd
 priority=3
 autostart=false
 autorestart=false