workloadmanager: propagate CodeInterpreter template metadata to warm pool pods

[CapThunder19]

What type of PR is this

/kind bug

What this PR does / why we need it

When warmPoolSize > 0, a CodeInterpreter's template.labels and template.annotations never reached the sandbox pods. convertToPodTemplate built the SandboxTemplate's pod spec but left its metadata empty, so warm-pool pods were created without them. The direct (non-warm-pool) path already applies them, so turning on a warm pool silently changed what ended up on the pod

This PR

• sets ObjectMeta (labels and annotations) on the SandboxTemplate's pod template in convertToPodTemplate. The maps are copied so the informer-cached CodeInterpreter is never modified, and empty maps are stored as nil to match what the API server returns.
• makes podTemplateEqual compare metadata as well as the spec, so adding or changing labels on an existing CodeInterpreter updates its SandboxTemplate.

agent-sandbox already copies template metadata onto warm-pool pods, so no change is needed on that side.

Which issue(s) this PR fixes

Fixes #471

Special notes for your reviewer

• Tests: added table-driven unit tests covering metadata being copied, nil/empty maps, the cached object not being mutated, a new template getting metadata, an existing template being updated when only metadata changes, and no update for CodeInterpreters without metadata. The new metadata tests fail without the fix, and go test ./pkg/workloadmanager/ passes. I couldn't run make lint locally (Windows), so I'm relying on CI for that.
• Existing CodeInterpreters that already set template labels or annotations will get their SandboxTemplate updated after upgrade, so agent-sandbox may recreate their warm-pool pods once. CodeInterpreters without template metadata are not affected.
• I left the container name as is. It's codeinterpreter in the warm-pool path and code-interpreter in the direct path. Renaming it would change every existing SandboxTemplate and recreate everyone's warm-pool pods, so I think it's better done separately if we want it

Does this PR introduce a user-facing change?

CodeInterpreter template labels and annotations are now applied to warm pool sandbox pods, matching the behavior when no warm pool is used.

[volcano-sh-bot]

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[volcano-sh-bot]

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Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 60.28%. Comparing base (5903457) to head (1a6c5f8).
⚠️ Report is 16 commits behind head on main.
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Additional details and impacted files

@@            Coverage Diff             @@
##             main     #474      +/-   ##
==========================================
+ Coverage   59.98%   60.28%   +0.29%     
==========================================
  Files          36       35       -1     
  Lines        3589     3626      +37     
==========================================
+ Hits         2153     2186      +33     
- Misses       1216     1218       +2     
- Partials      220      222       +2     

Flag	Coverage Δ
unittests	60.28% <100.00%> (+0.29%)	⬆️

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