Graceful eviction umbrella issue

[RainbowMango]

What would you like to be added:
We hope to introduce a graceful way to delay the removal until the resource is available on the substitute cluster.

Iterated task:

• API change #2273
• Introduce GracefulEviction feature gate. #2340
• Make changes to karmada-scheduler to mark schedulerObservedGeneration (RB) #2330
• Make changes to karmada-scheduler to mark schedulerObservedGeneration (CRB) #2345
• Introduce grace-eviction-controller to implementers the API. (#2319)
• Make changes to binding controller to adopt the changes. (#2339)
• Make changes to taint manager to trigger graceful eviction. (#2346)
• Introduce a documentation to https://karmada.io/docs/next/ (under Multi-cluster scheduling)

Why is this needed:
#1762 addresses the eviction feature that focuses on trigger eviction based on taints toleration and introduces a taint manager to perform the eviction.

Once the taint manager performs the eviction (means remove a specific cluster from the RB(ResourceBinding) target list(.spec.clusters)), the resource referenced by the RB will be `removed immediately from the target cluster.

For example, there is an online workload(like an Nginx server) that was running on cluster-1, and then a network broken issue happens, Karmada starts to evict it from cluster-1 and probably karmada-scheuler scheduled it to cluster-2. The thing is the workload would be removed immediately and no service available until the workload runs on cluster-2.

[XiShanYongYe-Chang]

I will continuously improve failover.
/close

[karmada-bot]

@XiShanYongYe-Chang: Closing this issue.

In response to this:

I will continuously improve failover.
/close

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