Automatic merge from submit-queue (batch tested with PRs 62063, 62169, 62155, 62139, 61445). If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.
Schedule even if extender is not available when using extender
**What this PR does / why we need it**:
When using scheduler extender, if the extender is not available scheduling of all pods fail.
We should let the scheduling happen but display error message that extender is failing.
`IsIgnorable()` is added to extender to indicate: if scheduling of all pods should fail when it's unavailable
**Backward compabtiility:**
We use `IsIgnorable` instead of `IsCritical` so that when this flag is not set, the default value will be `false`, i.e. not ignorable, which consistent with the current behavior in existing extenders.
**Which issue(s) this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close the issue(s) when PR gets merged)*:
Fixes: #60616
**Special notes for your reviewer**:
kindly cc @ravisantoshgudimetla to see if this meets your expectation
TODO: update the examples in kubernetes/examples, but the strategy there is not clear to me for now
**Release note**:
```release-note
Schedule even if extender is not available when using extender
```
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