Introduce a mechanism to actively trigger rescheduling

[chaosi-zju]

What would you like to be added:

Introducing a mechanism of actively triggering rescheduling.

Why is this needed:

Proposal of introducing a rebalance mechanism to actively trigger rescheduling of resource.

Assuming the user has propagated the workloads to member clusters, in some scenarios the current replicas distribution
is not the most expected, such as:

• replicas migrated due to cluster failover, while now cluster recovered.
• replicas migrated due to application-level failover, while now each cluster has sufficient resources to run the replicas.
• as for Aggregated schedule strategy, replicas were initially distributed across multiple clusters due to resource
  constraints, but now one cluster is enough to accommodate all replicas.

Therefore, the user desires for an approach to trigger rescheduling so that the replicas distribution can do a rebalance.

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The issue is created to track all related activities：

Proposal：

• • Proposal of introducing a rebalance mechanism to actively trigger rescheduling of resource #4698

Implementation：

• • Scheduler: Introduce a mechanism to scheduler to actively trigger rescheduling #4848
• • WorkloadRebalancer：Introduce a new API named WorkloadRebalancer to support rescheduling #4841
• • Webhook: Introduce a validation webhook to prohibit WorkloadRebalancer from being modified #4859
• • bugfix: fix patching WorkloadRebalancer failed due to misuse of shared slices #4875
• • Support update: feat: support update event in WorkloadRebalancer #4860
• • Support auto delete: support auto delete WorkloadRebalancer when time up #4894

UT

• • add ut for WorkloadRebalancer controller #4876

E2E Test：

• • add e2e for WorkloadRebalancer #4869
• • add more e2e for WorkloadRebalancer #4961

Doc of Best Practice：

• • en tutorial: add userguide for workload-rebalancer website#608
• • zh tutorial:
• • en user guide: add tutorial for workload-rebalancer website#612
• • zh user guide:

[RainbowMango]

We need a document for this feature that is missing from this umbrella issue.

[RainbowMango]

FYI
Add two tasks for the zh documents.