fix(sandboxclaim): avoid claim identity collisions

[chacha923]

Ⅰ. Describe what this PR does

This PR fixes SandboxClaim claimed-sandbox counting so a claim is identified by both internal claim-name bookkeeping and the claim UID.

The previous flow could become unstable because agents.kruise.io/claim-name is an internal label but user-provided spec.labels could override it, while claimed-sandbox recovery did not narrow the cache query by claim name. This could make recreated same-name claims or later reconciliations report incorrect ClaimedReplicas.

Key changes:

1. Add a claim-name sandbox cache index and extend ListSandboxesOptions with ClaimName.
2. Apply claim-name filtering together with the existing claim UID owner filter in ListSandboxes and CountActiveSandboxes.
3. Pass ClaimName: claim.Name from SandboxClaim claimed-sandbox recovery.
4. Preserve the internal agents.kruise.io/claim-name label after applying user labels so spec.labels cannot override it.
5. Add regression tests for recreated same-name claims, combined claim-name/UID filtering, dead sandbox exclusion, and user-provided claim-name label overrides.

Ⅱ. Does this pull request fix one issue?

Fixes #311

Ⅲ. Describe how to verify it

go test -count=1 ./pkg/cache/... ./pkg/controller/sandboxclaim/core/...
git diff --check

Ⅳ. Special notes for reviews

• No CRD/API changes are introduced, so make generate and make manifests are not required.
• The new claim-name index is registered through GetIndexFuncs, keeping production cache and test cache index definitions consistent.

[kruise-bot]

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[codecov]

Codecov Report

❌ Patch coverage is 90.90909% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 79.96%. Comparing base (3a3000b) to head (c9a1771).

Files with missing lines	Patch %	Lines
pkg/cache/cache.go	84.61%	0 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #590      +/-   ##
==========================================
+ Coverage   79.94%   79.96%   +0.02%     
==========================================
  Files         202      202              
  Lines       14883    14902      +19     
==========================================
+ Hits        11898    11917      +19     
  Misses       2556     2556              
  Partials      429      429              

Flag	Coverage Δ
unittests	79.96% <90.90%> (+0.02%)	⬆️

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