fix IPAM allocation caused by incorrect pod annotations patch

[zhangzujian]

• Make sure you have followed Kube-OVN Code Style.

What type of this PR

• Bug fixes

Which issue(s) this PR fixes:

Fixes #2611 introduced in #2563

WHAT

🤖 Generated by Copilot at 34d6019

Improve error handling and pod caching in pod.go. Return pod object from reconcileAllocateSubnets and use it to update or recycle pod resources. Handle pod deletion cases more robustly.

🤖 Generated by Copilot at 34d6019

Oh we're the brave coders of the Kubernetes sea
And we handle errors and pods with skill and glee
We reconcileAllocateSubnets and handleAddOrUpdatePod
And we heave ho, heave ho, on the count of three

HOW

🤖 Generated by Copilot at 34d6019

• Modify handleAddOrUpdatePod to handle pod object and error returned by reconcileAllocateSubnets (link)
• Change reconcileAllocateSubnets signature to return pod object and error (link)
• Return pod object and error in reconcileAllocateSubnets when various operations fail (link, link, link, link, link, link, link)
• Return pod object and error in reconcileAllocateSubnets when no error occurs (link)

[github-actions]

• The commit message should be more descriptive and informative. It should explain what changes are being made and why they are necessary.
• In the handleAddOrUpdatePod function, the comment "check if route subnet is need" should be corrected to "check if route subnet is needed".
• In the reconcileAllocateSubnets function, the parameters cachedPod and pod should have their types specified.
• In the reconcileAllocateSubnets function, the return type should be specified in the function signature instead of being returned as a tuple.
• In the reconcileAllocateSubnets function, the error messages should be more specific and informative. They should indicate which operation failed and why.
• In the reconcileAllocateSubnets function, the patchedPod variable should be checked for nil before calling the DeepCopy() method on it to avoid a panic.

[oilbeater]

LGTM, but I was wondering if we should replace patch with update to avoid such conflict. Maybe there are still issues when the cache is diverge from the apiserver but the patch will still update the pod annotations.