[WIP] Reclaim backoff for re-borrowing after preemption-driven reclamation

[hahahaheihei]

What type of PR is this?

/kind feature
/kind api-change

What this PR does / why we need it:

Implements the reclaim backoff proposed in KEP-14468 (design review in progress). After a ClusterQueue's borrowed resource is reclaimed by cohort preemption, the scheduler applies an exponentially growing cooldown during which it defers only the flavor assignments that would borrow that same resource again. This breaks the "admitted, then immediately reclaimed again" spin loop without changing quota semantics for well-behaved workloads.

The feature is opt-in via a new reclaimBackoff block in the v1beta2 Configuration API and disabled by default.

/hold

Hold until the KEP is accepted.

Which issue(s) this PR fixes:

Part of #14468

Special notes for your reviewer:

KEP under review: #14469

Submitted as a draft reference implementation to aid the KEP discussion. Verified locally: make verify, unit tests, the new integration suite (test/integration/singlecluster/scheduler/reclaimbackoff), and the e2e baseline (62/62) all pass.

Does this PR introduce a user-facing change?

Scheduling: Added an opt-in `reclaimBackoff` configuration that defers re-borrowing of a resource for an exponential cooldown after the ClusterQueue's borrowed share of that resource is reclaimed by preemption, breaking admit-reclaim spin loops.

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[kubernetes-prow]

Hi @hahahaheihei. Thanks for your PR.

I'm waiting for a kubernetes-sigs member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work.

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[kubernetes-prow]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: hahahaheihei
Once this PR has been reviewed and has the lgtm label, please assign mbobrovskyi, mimowo, pbundyra for approval. For more information see the Code Review Process.

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[tenzen-y]

/ok-to-test

[kubernetes-prow]

PR needs rebase.

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