Automatic merge from submit-queue (batch tested with PRs 49409, 49352, 49266, 48418)
Fix duplication in scheduler.
**What this PR does / why we need it**:
This fixes duplicate code in scheduler.
**Which issue this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close that issue when PR gets merged)*: fixes #
No issue.
**Special notes for your reviewer**:
**Release note**:
```release-note
```
@kubernetes/sig-scheduling-pr-reviews @bsalamat
Previously, the scheduler created two separate list watchers. This
changes the scheduler to be able to leverage a shared informer, whether
passed in externally or spawned using the new in place method. This
removes the last use of a "special" informer in the codebase.
Allows someone wrapping the scheduler to use a shared informer if they
have more information avaliable.
Where possible, switch the scheduler to use generated listers and
informers. There are still some places where it probably makes more
sense to use one-off reflectors/informers (listing/watching just a
single node, listing/watching scheduled & unscheduled pods using a field
selector).
