fix addAnnotationWithClusterName crash

[ikaven1024]

What type of PR is this?
/kind bug

What this PR does / why we need it:

Which issue(s) this PR fixes:
Fixes #3960

Special notes for your reviewer:

When listing from an Infromer, it returns reference of objects in cache.

karmada/vendor/k8s.io/client-go/tools/cache/thread_safe_store.go

Lines 245 to 253 in 48a37ab

	func (c *threadSafeMap) List() []interface{} {
	c.lock.RLock()
	defer c.lock.RUnlock()
	list := make([]interface{}, 0, len(c.items))
	for _, item := range c.items {
	list = append(list, item)
	}
	return list
	}

When two or more search requests come at the same time, and all requests list objects from informer and add cluster annotation into the same objecs, it raises crash.

karmada/pkg/registry/search/storage/cache.go

Line 141 in 5763248

items = append(items, addAnnotationWithClusterName(cloneObjects, cluster.Name)...)

Does this PR introduce a user-facing change?:

`karmada-search`: Fixed a panic due to concurrent mutating objects in the informer cache.

[codecov-commenter]

Codecov Report

Merging #3966 (5763248) into master (48a37ab) will decrease coverage by 0.04%.
The diff coverage is 0.00%.

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@@            Coverage Diff             @@
##           master    #3966      +/-   ##
==========================================
- Coverage   54.81%   54.78%   -0.04%     
==========================================
  Files         232      232              
  Lines       22521    22525       +4     
==========================================
- Hits        12345    12340       -5     
- Misses       9499     9508       +9     
  Partials      677      677              

Flag	Coverage Δ
unittests	54.78% <0.00%> (-0.04%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files Changed	Coverage Δ
pkg/registry/search/storage/cache.go	0.00% <0.00%> (ø)

... and 2 files with indirect coverage changes

[RainbowMango]

/assign

@ikaven1024 Thank you so much for the quick response and hard work!

[RainbowMango]

/lgtm
/approve

[karmada-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: RainbowMango

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• pkg/registry/OWNERS [RainbowMango]

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[RainbowMango]

Just opened #3968 to track the backport tasks.