KEP-6268: Stall and resume slow watch streams instead of terminating them

[nami-ant]

• One-line PR description: Add provisional KEP-6268 for the WatchCacheStallResume feature gate.
• Issue link: Stall and resume slow watch streams instead of terminating them (WatchCacheStallResume) #6268
• Other comments:

This adds the provisional KEP for WatchCacheStallResume (sig-api-machinery, alpha): when a watch's delivery buffer fills, park the watch and resume it from the watch cache history instead of force-closing it, so a slow or stalled watch client no longer delays or force-closes healthy watchers. A watch is terminated only when its resume position has aged out of the history (an honest 410 Gone). Off by default.

Implementation PR: kubernetes/kubernetes#141228

Draft pending KEP-approver / PRR review; happy to iterate on the design and PRR details here.

/sig api-machinery
/kind kep

[linux-foundation-easycla]

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• ✅ login: nami-ant / name: Nami Nasserazad (9b2b9db)

[kubernetes-prow]

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[kubernetes-prow]

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[nami-ant]

/easycla