Now, when unschedulable Pods are updated, the scheduling queue checks with QueueingHint(s) whether the update may make the pods schedulable, and requeues them to activeQ/backoffQ **only when** at least one QueueingHint(s) return Queue. 
  
  Action required for custom scheduler plugin developers:

- The scheduling queue didn't notice any extenders' failures, it could miss some cluster events,
  and it could end up Pods rejected by Extenders stuck in unschedulable pod pool in 5min in the worst-case scenario.

### Scheduling

- Improved fairness of the scheduling queue by placing pods which are attempted recently behind other pods with the same priority. ([#73700](https://github.com/kubernetes/kubernetes/pull/73700), [@denkensk](https://github.com/denkensk))

- Fixes the bug in PodTopologySpread that only happens with QHint enabled, 

- The scheduling queue didn't notice any extenders' failures, it could miss some cluster events,
  and it could end up Pods rejected by Extenders stuck in unschedulable pod pool in 5min in the worst-case scenario.

- The scheduling queue didn't notice any extenders' failures, it could miss some cluster events,
  and it could end up Pods rejected by Extenders stuck in unschedulable pod pool in 5min in the worst-case scenario.

- The scheduling queue didn't notice any extenders' failures, it could miss some cluster events,
  and it could end up Pods rejected by Extenders stuck in unschedulable pod pool in 5min in the worst-case scenario.

- The scheduling queue didn't notice any extenders' failures, it could miss some cluster events,
  and it could end up Pods rejected by Extenders stuck in unschedulable pod pool in 5min in the worst-case scenario.

      <match value="0x00053162" type="little32" offset="12"/>
    </magic>
    <sub-class-of type="application/x-berkeley-db"/>
  </mime-type>
  <mime-type type="application/x-berkeley-db;format=queue">
    <_comment>Berkeley DB Queue Database</_comment>
    <magic priority="50">
      <match value="0x00042253" type="host32" offset="12"/>
      <match value="0x00042253" type="big32" offset="12"/>

pkg syscall (netbsd-arm64-cgo), func Kevent(int, []Kevent_t, []Kevent_t, *Timespec) (int, error)
pkg syscall (netbsd-arm64-cgo), func Kill(int, Signal) error
pkg syscall (netbsd-arm64-cgo), func Kqueue() (int, error)
pkg syscall (netbsd-arm64-cgo), func Listen(int, int) error
pkg syscall (netbsd-arm64-cgo), func Lstat(string, *Stat_t) error
pkg syscall (netbsd-arm64-cgo), func Mkfifo(string, uint32) error