api(failover): Add EvictionQueueOptions to configure dynamic rate limit

[whosefriendA]

What type of PR is this?
/kind api-change

What this PR does / why we need it:

Which issue(s) this PR fixes:
part of #6746

Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

API Change: Added four new fields to the GracefulEvictionPolicy for advanced rate control:
- `resourceEvictionRate`: default eviction rate when the system is healthy.
- `secondaryResourceEvictionRate`: fallback rate when too many clusters are unhealthy.
- `unhealthyClusterThreshold`: threshold ratio of unhealthy clusters triggering downgrade.
- `largeClusterNumThreshold`: cluster number threshold to adjust eviction behavior in large-scale instances.

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[gemini-code-assist]

Summary of Changes

Hello @whosefriendA, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request enhances the failover mechanism within the controller manager by introducing dynamic rate limiting for resource eviction. It provides new configuration parameters that allow administrators to define primary and secondary eviction rates, as well as thresholds for cluster health and scale. These parameters enable the system to intelligently adjust eviction speeds based on the current state of the Karmada instance, aiming to prevent aggressive evictions during periods of instability or in large-scale deployments, thereby improving overall system resilience.

Highlights

• Dynamic Resource Eviction Rate Limiting: Introduces new configuration options to dynamically adjust the rate at which resources are evicted during failover scenarios, enhancing system stability.
• Configurable Eviction Rates: Adds ResourceEvictionRate and SecondaryResourceEvictionRate to define default and reduced eviction speeds, respectively.
• Health-Based Rate Adjustment: Implements UnhealthyClusterThreshold to automatically switch to the secondary eviction rate when a significant portion of clusters are unhealthy.
• Scale-Aware Eviction Behavior: Adds LargeClusterNumThreshold to modify eviction strategies for large-scale Karmada instances, potentially halting eviction for smaller, unhealthy instances.

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[gemini-code-assist]

Code Review

This pull request introduces new configuration options to FailoverOptions for dynamic rate limiting of evictions. Note that the PR title mentions EvictionQueueOptions, but the changes are made to FailoverOptions. The changes add new fields to the struct and corresponding command-line flags. My review focuses on the correctness and clarity of these new API additions.

I've identified a high-severity issue regarding the lack of validation for the new options, which could lead to unexpected behavior if invalid values are provided. I've also suggested a medium-severity improvement to the help text of one of the new flags for better user clarity. Overall, the changes are a good step towards implementing dynamic eviction rate limiting, but the validation aspect needs to be addressed before this can be considered complete.

[codecov-commenter]

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Codecov Report

❌ Patch coverage is 9.67742% with 28 lines in your changes missing coverage. Please review.
✅ Project coverage is 45.82%. Comparing base (64428fa) to head (88023ac).

Files with missing lines	Patch %	Lines
cmd/controller-manager/app/options/failover.go	9.67%	24 Missing and 4 partials ⚠️
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Additional details and impacted files

@@            Coverage Diff             @@
##           master    #6777      +/-   ##
==========================================
- Coverage   45.84%   45.82%   -0.03%     
==========================================
  Files         690      690              
  Lines       57300    57330      +30     
==========================================
+ Hits        26271    26273       +2     
- Misses      29399    29423      +24     
- Partials     1630     1634       +4     

Flag	Coverage Δ
unittests	45.82% <9.67%> (-0.03%)	⬇️

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[XiShanYongYe-Chang]

1. The title appears incomplete; it can be adjusted.
2. It can link the umbrella issue in Which issue(s) this PR fixes. like this: part of #xxxx
3. Fill in the release note as hint.

Other PRs can also be adjusted in this way.

[XiShanYongYe-Chang]

1. The title appears incomplete; it can be adjusted.
2. It can link the umbrella issue in Which issue(s) this PR fixes. like this: part of #xxxx
3. Fill in the release note as hint.

Other PRs can also be adjusted in this way.

Hi @whosefriendA, can you help fix it and squash the commit into one?