Shortest job first scheduling for server mode

[soodoshll]

Motivation: All requests have the same share in final score, so we prioritize shorter jobs.

====================================================================================================
Job             All2All Backend                QPS      99% Lat (ms)    99% Lat (s)  Result
====================================================================================================
fcfs        flashinfer_all2allv            12.07    13,267.77       13.27        INVALID
sjf         flashinfer_all2allv            12.07    11,809.73       11.81        VALID
====================================================================================================

Best 99% latency: flashinfer_all2allv (11.81s)
Worst 99% latency: flashinfer_all2allv (13.27s)
Improvement: 11.0%

[wangshangsam]

Thanks a lot, @soodoshll ! Which flag to enable this?