[core] Simplify scheduling_queue.go

[asm582]

We need to simplify scheduling_queue.go, the file I think has been overdone to avoid race conditions. at most two threads move AW objects within MCAD's internal queues. we need to re-implement some of the features to simplify the logic of internal queuing and locking.

[asm582]

PR has been merged where the code was redesigned and simplified.