feat(sandboxid): implement core short sandbox ID logic

[singhsrijan46]

Ⅰ. Describe what this PR does

This pull request introduces the core sandboxid package and lays the groundwork for supporting short, stable Sandbox IDs as specified in the design spec:

1. Schema Constant: Added LabelSandboxID (agents.kruise.io/sandbox-id) to api/v1alpha1/sandboxset_types.go.
2. Short ID Generation & Resolution (sandboxid package):
   • Implemented Base32 lowercase 26-character encoding (GenerateShort) to authoritatively map Sandbox UID to a DNS-safe label.
   • Implemented ID resolution (Resolve) which resolves using the short ID label with a fallback to the deterministically-formatted legacy ID (<namespace>--<name>).
   • Implemented metadata label assignment helper (AssignShort).
3. Metadata Reset Preservation: Refined resetMetadataForPool in pkg/controller/sandbox/core/recycle.go to explicitly preserve LabelSandboxID during sandbox recycling.
4. Flaky Test Fixes: Resolved flaky strict timing assertions (assert.Greater vs assert.GreaterOrEqual) in pkg/sandbox-manager/infra/sandboxcr/claim_test.go and clone_test.go where fast mock clocks or immediate rate limit error returns yielded exactly 0s wait times.

Ⅱ. Does this pull request fix one issue?

NONE

Ⅲ. Describe how to verify it

Unit tests have been added and verified:

1. Core Sandbox ID Tests: go test -v ./pkg/sandbox-manager/sandboxid/...
2. Recycle Metadata Reset Tests: go test -v ./pkg/controller/sandbox/core/...
3. Sandbox CR Infra Claim/Clone Tests: go test -v ./pkg/sandbox-manager/infra/sandboxcr/...

Ⅳ. Special notes for reviews

The timing assertions for Wait and WaitReady metrics in sandboxcr were adjusted to assert.GreaterOrEqual to eliminate flakes on fast test runners/environments.

[kruise-bot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

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Details

Needs approval from an approver in each of these files:

• api/OWNERS
• pkg/controller/OWNERS
• pkg/sandbox-manager/OWNERS

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 80.08%. Comparing base (bc355be) to head (36a4416).

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #657      +/-   ##
==========================================
+ Coverage   80.06%   80.08%   +0.01%     
==========================================
  Files         229      230       +1     
  Lines       17862    17895      +33     
==========================================
+ Hits        14302    14332      +30     
- Misses       2975     2978       +3     
  Partials      585      585              

Flag	Coverage Δ
unittests	80.08% <100.00%> (+0.01%)	⬆️

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