Graduate elastic indexed job to stable

[ahg-g]

• One-line PR description: graduate to stable

• Issue link: Elastic Indexed Jobs #3715

• Other comments:

[wojtek-t]

Please switch back to me - we're generally not changing approvers in the middle.

[wojtek-t]

BTW - the only comment I have about PRR is the upgrade->downgrade->upgrade tests.
Please update it.

[I'm fine with saying that given the feature effectively is only relaxing validation (so is purely in-memory), upgrade/downgrade boils down to actual feature tests.

[ahg-g]

sg, done.

[wojtek-t]

/assign @soltysh
/assign

[wojtek-t]

/approve PRR

[soltysh]

Several minor nits.

/approve
from sig-apps pov

[soltysh]

Several minor nits:

• in ### Version Skew Strategy you could copy the same answer as you have in ###### Can the feature be disabled once it has been enabled (i.e. can we roll back the enablement)? section or ###### What are other known failure modes? (linking to them is also fine).
• in ###### Are there any tests for feature enablement/disablement? you have N/A, but you could actually link to https://github.com/kubernetes/kubernetes/blob/a06568062c41b4f0f903dcb78aa6ea348bbdecfc/test/integration/job/job_test.go#L2746
• please update ## Implementation History

[ahg-g]

thanks, done

[soltysh]

/lgtm

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: ahg-g, soltysh, wojtek-t

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• keps/prod-readiness/OWNERS [soltysh,wojtek-t]
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