a drift behavior as an eventual disruption should documentation

[flavono123]

Description

How can the docs be improved?

for now, the doc says drift is the one of method of graceful disruption with the other consolidation methods:
https://github.com/kubernetes-sigs/karpenter/blob/81481b742d64a91739c22290c042218244737896/pkg/controllers/disruption/types.go#L98-L99

actually a disruption by drift do not gracefully:
https://github.com/kubernetes-sigs/karpenter/blob/81481b742d64a91739c22290c042218244737896/pkg/controllers/disruption/types.go#L98-L99

the class is eventual(i think controller does 'immediately', btw) and other consolidation methods are graceful.

document should say that drift is not a graceful method.

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[jmdeal]

Graceful disruption means something different in this context. In the docs we distinguish between graceful and forceful disruption. Forceful disruption will occur as soon as the triggering event occurs (e.g. the NodeClaim expired or there was a spot interruption message). Graceful disruption means that it can be blocked by other conditions (e.g. node disruption budgets, blocking PDBs, and the do-not-disrupt annotation). In this context, both drift and consolidation are graceful.

Drift does have some additional interactions with TerminationGracePeriod. If a NodeClaim has a TGP set and it has been drifted, Karpenter won't block disruption on PDBs or the do-not-disrupt annotation. Node disruption budgets are still respected, differentiating it from forceful disruption. This should have been documented in the disruption docs under the TGP and pod level controls docs, but does not appear to be. The "eventual" disruption class is an internal concept and shouldn't be documented directly, but the docs should be updated to clarify drift's interaction with TGP.