Rolling restart workers

[tagomoris]

Of course, It should be implemented after #1386.

[daipom]

Zero downtime restart feature is supported on v1.18.0

• SIGUSR2: zero downtime restart #4624

This feature may have different benefits, but since there have been no updates for a while, and it is unclear what specific issues need to be resolved with the latest version, we are closing it.
If a similar feature seems necessary again in the latest version, please feel free to recreate or reopen.