Wait for search multiClusterCache ReadinessCheck success

[XiShanYongYe-Chang]

What type of PR is this?

/kind cleanup
/kind feature

What this PR does / why we need it:

To adapt to new features of the Kubernetes community: Resilient Watchcache Initialization, we also need to modify the Karmada-search component because we also use the same cache.

After the Karmada-search component is started, PostStartHook is added to wait for the cache to be ready. In addition, related ut is modified.

Which issue(s) this PR fixes:
Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

karmada-search: Implement search proxy cache initialization post-start-hook

[XiShanYongYe-Chang]

/cc @RainbowMango @ikaven1024

[codecov-commenter]

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Codecov Report

Attention: Patch coverage is 48.71795% with 40 lines in your changes missing coverage. Please review.

Project coverage is 46.31%. Comparing base (c950edd) to head (9367ca9).
Report is 12 commits behind head on master.

Files with missing lines	Patch %	Lines
pkg/search/proxy/controller.go	34.78%	15 Missing ⚠️
cmd/karmada-search/app/options/options.go	0.00%	13 Missing ⚠️
cmd/karmada-search/app/karmada-search.go	0.00%	9 Missing ⚠️
pkg/search/proxy/testing/mock_store.go	0.00%	2 Missing ⚠️
cmd/karmada-search/app/options/validation.go	0.00%	1 Missing ⚠️

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Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5846      +/-   ##
==========================================
+ Coverage   46.03%   46.31%   +0.28%     
==========================================
  Files         660      661       +1     
  Lines       53987    54364     +377     
==========================================
+ Hits        24851    25177     +326     
- Misses      27519    27562      +43     
- Partials     1617     1625       +8     

Flag	Coverage Δ
unittests	46.31% <48.71%> (+0.28%)	⬆️

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[RainbowMango]

/lgtm
/approve

[karmada-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: RainbowMango

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Needs approval from an approver in each of these files:

• cmd/karmada-search/OWNERS [RainbowMango]
• pkg/search/OWNERS [RainbowMango]

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